是指一次吃不多，吃不完。可以表达为：“一次并不能吃很多”或者“一次吃得较少”。“多少”在这里不表疑问。不知道能不能帮到你。

It means you can't eat a lot at a time.I don't know wether you can understand or not.My English is poor.I'm soooo sorry_(:з」∠)_

if you prepared a lot of food as dinner for your friend, he/she would say so, meaning we can't eat that much food at one time. Or in other situation, you are preparing food for the following two days but you are not sure whether you have prepared enough, so you asked your friend whether it is enough or not. He/she will say so, meaning that is enough because we will not eat a lot in one meal.

It means you are not able to eat too much at a time. Let's say your friend brings you a lot of homemade cookies but they will go stale if you don't eat them up soon. So you suggest your friend taking back some of the cookies and say "一次吃不了多少".

一次 并 吃不了 多少 = даже на один раз поесть не хватит