I guess you're refering to
GetBlockSubsidy() function.
nSubsidy is the number of coin "mined".
nHeight is the block number.
Here you're just telling the function to reward "10000" coins for the first block (provided that you're returning this value).
Given what you asked, a more comprehensible way to achieve the same result would be :
nSubsidy = (nHeight == 1) ?
10000 * COIN :
100 * COIN;
Also, not sure, but the first block is probably 0 (nHeight)