A bull will that size will eat multiple weanling rats, and still look for more...that doesn't mean you should feed them that way. Like with many things in this hobby, the question of how big, how much, and how often to feed will get you almost as many different answers as respondants. I feed my adult bulls mice, rats of various sizes (pinks to mediums), hamsters, gerbils, ASFs...basically, whatever I have in the freezers that I don't deem too big for them. I don't like giving them large prey items, but that doesn't mean I give them a bunch of small ones.
I generally only give one or two prey items per feeding (well, unless I'm giving rat pinks to a 6 ft adult...then I throw them a handful - just like they would get if they came across a nest). I also don't hold to a set feeding schedule. I might shoot for a 10 day interval, but go 14 days one time, and 5 the next...and if I have extra stuff defrosted from other feedings, well, a bullsnake is one of the most likely recipients.
Two weanling rats is a small meal for a good sized bull; but, if those meals are coming regularly, they'll be sufficient. If the bull is maintaining good body weight, don't worry too much about it...if it starts looking thin, increases the feeding. (Another sure clue is when they shoot out of the enclosure like a mouth opened rocket, lol)