Recieved and tabulated (counted) are two entirely diff things.
Once your mailed-in vote is put into the computer, you have voted. Just because it's received at the Supervisor of Elections office does NOT mean it has been tabulated (counted).
INPERSON voting overrides mailed in ballots. Period.
Once employees go thru the motion of opening the mailed in ballot, they CHECK to see if the person has already voted. If the computer says they voted IN PERSON, the mailed in ballot is thrown out. If the computer says they have not voted, their status (to vote) is verified and the ballot is THEN tabulated (counted) in the system.
Checks and balances.
FYI- not all states give receipts. FL does not.(At least my county does not.)