It has to do with Form 1040 Line 30 Recovery Rebate Credit.

In our case, we received EIP1 of 2900 (dad 1200,mom 1200,daughter 500, son 0) and EIP2 of 2400(dad 600, mom 600, daughter 600, son 600).  Our tax software asked us for EIP1 and EIP2 payments and calculated that we were eligible for 500 for first round since we did not receive 500 for our son on first round.  Our Form 1040 shows 500. on Line 30.

Edit to add:
I assumed the Covid relief for the farm would be considered farm income but that the personal checks would be tax-free. Is this correct?
Yes, the CFAP payments are treated as Government Program Payments and you should have received a 1099 from the FSA.
The personal checks are the numbers used for calculating Form 1040 Line 30.