Counts in spectrometer

Fpmagnani

Well, I'm not a physician so, maybe my doubt is a little fool. Well, I'm mapping the light emitted by some lamps in some aquariums. For that, I'using a spectrometer named Ocean Optics USB4000 and a software named SpectraSuite. My intention is to discover how much is the total light getting into the aquariums and haw is it distributed in the aquarium. After taking the measurements, i will interpolate the data in the software Voxler from goldensoftware.
Well, my problem is in the beginning of these processes: the data that the spectrometer take is given by counts in each kind of wave, like that:
Wave Counts
178,91 -30,32
179,13 -30,32
179,34 -30,32
179,56 -47,11
179,78 -52,23
180,00 25,59
180,21 -3,29
180,43 4,70
180,65 56,92
180,86 -16,19
181,08 4,13
181,30 6,32
181,51 10,22
181,73 13,86
181,95 18,10
182,17 22,35
182,38 22,55
182,60 23,71
182,82 24,45
183,03 21,25
183,25 23,55
183,47 23,24
183,68 25,75
183,90 26,41
184,12 26,91
184,34 26,41
184,55 29,11
184,77 29,52
184,99 30,15
185,20 31,23
185,42 31,96
185,64 31,48
(...........................)
880,40 239,06
880,57 228,80
880,74 222,27
880,91 213,25
881,07 207,39
881,24 199,64
881,41 191,34
881,58 185,91
881,74 182,21
881,91 176,63
882,08 170,85
882,25 165,77
882,42 163,48
882,58 161,57
882,75 159,43
882,92 158,30
883,09 158,19
883,25 156,41
883,42 155,53
883,59 154,07
883,76 150,13
883,92 149,86
884,09 150,75
884,26 147,37
884,43 148,47
884,60 147,10
884,76 147,05
884,93 147,07
885,10 145,44
885,27 145,20
885,43 144,78
885,60 145,16
885,77 143,63
885,93 142,32
886,10 142,19
886,27 143,42
886,44 142,82
886,60 142,32
886,77 143,33
886,94 143,85
887,11 142,79
887,27 146,86
887,44 148,05
887,61 148,53
887,77 153,58
887,94 157,17
888,11 145,19
888,28 145,60
888,44 154,82
888,61 164,44
888,78 136,79
888,94 203,56
889,11 196,60
889,28 169,77
889,45 229,98
889,61 215,23

As you can see, there are even negative counts and I'm not getting really well what is the meaning of these "counts" and how can i convert it to any optic unites.