I agree. There are too many plants in that pot. If that is a #1 nursery pot, 6 inches across at the top x 8 inches deep, it should hold one garlic plant. A garlic plant's root system is pretty massive.
The ultimate size of a garlic bulb you grow will also depend in part on how large the clove is that you planted. All other things being equal, a larger clove to begin with will yield a larger harvest bulb.
