You'll have to look around using the info only you can see. Examples:

https://turbotax.intuit.com/tax-tips/irs-tax-return/what-is-the-difference-between-agi-and-magi-on-y...

https://proconnect.intuit.com/community/proseries-tax-discussions/discussion/another-new-unemploymen...

"What is getting added back in to make the MAGI equal $105,951?"

LOOK at the return.  Any professional preparer should be able to follow the money on a return to see where items come from and where they belong....if you cant do that, how can you tell if a return is complete and correct?