Background
The usual way MCNP works is to give you tallies on the basis of "per particle started." So, whatever you are tallying, say energy deposited in a target, you get the result per particle started. Then your normalize by multiplying by the number of particle per second in your source. Your source appears to be 87357 particles per second.
I *think* the counting efficiency reports something about how many counts per second the detector can accommodate before it saturates. The detector acts on the basis of ionizing radiation increasing electric current flow. It might be in a crystal or a detector tube or some such. It has to recover between each event. The efficiency seems to report that it can handle 137 counts per second before saturating. So your count rate of 40 seems to be well within the capability of the counter. But you should check the user manual for your detector to be sure that is correct.
The next number seems to be reporting that you are observing 0.01 micro-Sieverts per hour. You have written microsilverperhour. So your detector reports dose in micro-Sieverts per hour. A Sievert is a measure of equivalent damage to tissue. Different types and energy of radiation produces different levels of damage to tissue.
https://en.wikipedia.org/wiki/Sievert
H = Q x D
Dose (H) is quality (Q) times energy deposited (D).
Doing Counts
It looks like your detector can report counts.
One thing you can do is just count particles that get to your detectors. There is a tally in MCNP that counts particles crossing a surface. Possibly your detector will have an information sheet that tells you the range of energies it is sensitive to and the size of the detector active part. (A tube or a crystal or some such.) So you can then count particles that make it to your detector from your source, and filter that according to the energy the detector is sensitive to. Probably you can use cutoffs in MCNP so that any particle that goes below the sensitive range of the detector is just deleted. That will save you some CPU time.
MCNP will then give you counts per particle started. You can then multiply that by your source activity, and result in counts per second. The numbers you wrote were counts = 40, and activity 87357. So, your MCNP tally should report 4.57E-4 counts per particle started so that when you multiply that by 87357 you get 40.
You can do a rough-and-ready self check for this. Get the size of the detector. Then just do an inverse square law to estimate that fraction of particles that should get from your source to your detector, without any of them getting absorbed by anything between. You have a detector with an area of (for example) 1 square cm. What distance away should it be so that the 1 cm^2 area is the correct fraction of the sphere to receive the correct fraction of particles? At a distance of 10 cm, for example, the sphere has an area of 1256 cm^2, so the 1 cm^2 detector sees 1/1256 of the total, or 7.96E-4. So I'm guessing you are holding your detector about 12 cm from the source.
Doing Dose in Micro-Sieverts
First you need the energy deposited per particle. This is straight forward in MCNP. You just tally the energy that gets deposited. It's an F6 tally if I recall correctly.
But then there is a quality multiplier. This takes into account the fact that different energy radiation produces different degree of harm to tissue. So, visible light is pretty much harmless. Soft x-ray does one level of damage. Hard x-ray another. If it were neutrons, another, etc.
One way to do this is to apply an average value for the range of radiation you are working with. That might be something you can look up in a radiation handbook that covers your source. Or you may have an information sheet for your source.
If you want to get really official with MCNP, you can apply a dose multiplier table. If you can get yourself a radiation dosimetry handbook, you can find such a table. That way you can multiply the quality factor right in MCNP. You get a table of multiplier values at each energy range, and apply that to the tally. That is the FM card in MCNP.
Again, the result will be per-particle-started. So you have a source of 87357 per second, or 3.1449E8 particles per hour.
So you tally energy deposited per particle started, and multiply by your quality factor to get micro-Sieverts dose per particle started. Watch those units because MCNP gives you the energy in MeV. And then you multiply by your particles per hour to get micro-Sieverts per hour. If that 0.01 micro-Sieverts per hour is your target, you should get something like 3.18E-11 micro-Sieverts per particle started.
