Educated guess here,
6 oz can (large) I would feed 1/2 in morning and 1/2 in evening.
1 can per day.

3 oz can (small) I would feed 2 cans a day to equal a 6 oz can.

Can food tends to be more fattening.

Only bad thing about all wet is the effect of cats teeth. The kibble keeps things cleaned and tarter free.