Expiation for one who has intercourse during the day in Ramadaan and the amount of food to be given

If a man has intercourse with his wife during the day in
Ramadaan, each of them must offer expiation, which is freeing a Muslim
slave. If they are unable to do that, then they must each fast for two
consecutive months if she was willing. If they are unable to do that then
they must feed sixty poor persons, each of them giving thirty saa’s of the
local staple food, one saa’ for each poor person, half on behalf of the man
and half on behalf of the woman, if they are unable to free a slave or fast.
They also have to make up the fast for the day on which intercourse took
place, and repent to Allaah and turn to Him, and regret it, and give it up,
and ask for forgiveness, because intercourse during the day in Ramadan is a
great evil and it is not permissible for anyone who is obliged to fast. End
quote. 

Majmoo’ Fataawa al-Shaykh Ibn Baaz
(15/302). 

Based on that, the amount of food that should be given to the
poor person is half a saa’ of rice etc., i.e., approximately one and half kilograms.