QTY is the total number of bombs dropped in a sequence, MULT defines how many are dropped at each pulse.
Dual racks will only release one at a time though.
QTY=2, MULT=2, will release two bombs as a pair.
QTY=4, MULT=2, INT=100, will release two pairs with 100ft of spacing.
QTY=4, MULT=1, INT=100, will release 4 single bombs with 100ft of spacing.