I think you will have to provide evidence of the ATM withdrawals for at least the previous two months when submitting your application to migraciones.
Clearly, the electronic system has resulted in changes since I got my residency. If you can only upload one ATM receipt, that is actually "easier" than providing the previous two months bank statements and all of the ATM receipts (showing withdrawals of enough ARS to meet the monthly requirement) when I first applied for residency. For the renewals I had to show the previous two months Argentine bank statements showing deposits that met the monthly income requirement and an updated letter (always with the Apostille) from a bank officer in the US confirming that I was still receiving the funds each month.I don't think that's quite right. At least it wasn't two years ago at the point the electronic system had just appeared. Things may be different now, but when I did it the system only allowed you to upload a single ATM receipt.
I only "discovered" when I requested the cambio de categoria to permanent residency on the third renewal that, as far as migraciones was concerned, I always had the visa pensionado, not the visa rentista.