To be more exact on this, I have already shown the number of cases divided by all cases ending at any place from 13th to 52nd. For example if the last heart is at the 51st place, the ratio is
50C12/52C13 =19%.
Let us suppose we put the final heart at the 13th place. Then how many ways can we fill 12 spots with 12 hearts? The answer in combinations is only 1. Now if the last heart was placed at the 14th spot, then we have 12 hearts to place in 13 places or this can be done in 13 ways.
Looking at it this way it is completely obvious that the more viable "space" that we have to maneuver the hearts in, the greater is the ratio of that case to all possibilities, referred to as the probability of that outcome. (Once we place a heart at position X then only the "space' before this placement is viable, we can not place anything after this point by definition of what we are supposedly doing.) Remember that all these ratios have to add up to covering all posibilities, and so sum to 1.
So that the question of what we are actually trying to do, or WHAT IS THE SAMPLE SPACE is extremely important. We have to define the characteristics of this sample space. That in itself, can be become confusing, and is the reason why it is best to try and clearly see how this sample space, i.e. all the combinations, can be ordered.