The base unit is how we calculate the total supply.
CAmount GetBlockSubsidy(int nHeight, const Consensus::Params& consensusParams)
{
int halvings = nHeight / consensusParams.nSubsidyHalvingInterval;
if (halvings >= 64)
return 0;
return 50 * COIN >> halvings;
}
The total supply is a function of the halving calculation.