My sons mother claimed our son on her 2019 return and received the stimulus payments for him. I'm claiming him on my 2020 return and don't know if I claim RRC or not?

When I fill out my info on the tax software I'm using, it ask if I want to find out if I am eligible for the recovery rebate credit. I didn't receive any credit for my son as his mother claimed him on her 2019 return. I received $1,200 on the first stimulus and $600 for the second one. I'm claiming him this year and when I enter that info, it says I'm eligible for $1,100 in RRC which I'm not sure if I'm supposed to or not. We are not married and alternate claiming him every year.