The amount for eating a morning snack before studying is like an egg or a little more and not eating much, but the main meal is after studying.
Sources: Ya'oi' Sukkah 10 11 Kdteim Bar Bi Rav, etc. who had tasted something before the study and entered the study, the rumors would not have continued after 6 hours of eating 18.
And as explained in the SS column, he bought Shacharit's tongue, he is the egg this fath, and eating a shaharit fath is only a little like the BHL SS bought it, and yet he eats a fath, while the time of the meal is in S. Kenez after that in the hours that follow.
And as explained in the order of the signs and the leadership in the Tosho'a signs, he bought a treasure, and for those in C, he bought 20, the column before he goes to B, he can eat a morning meal, etc., and in B, he bought 20, and then he will go about his business, etc., and in B, Kenz 20, and when the fourth hour comes, etc. And if it is 18, etc., he will wait until the sixth hour.
And here is this lesson of Kadteim Bar Bi Rav, etc. above 20 in Rashi there he tastes with his mouth full and drinks, and the lesson of eating Damiri there is like an egg Or a little more, as explained in Rambam and the rulings regarding the Sukkah there.
And Yaoi' in the explanation of the Sus Halacha bought that K. meant that he would eat at that time (we were in Fat Shacharit which I eat before the study) only a little.
מק"ט התשובה הוא: 4786