Are Time Machine backups limited as for the maximum size?

I'm trying to backup my 4TB macbook pro on an external backup unit. When the backup is almost complete (about 20 hours) I got this message

"Time Machine cannot complete the backup on 'TimeMachineBackup'. Time Machine partially completed the backup (94%) because there is not enough free space on the backup disk"

The external backup unit is 8TB and I just reformatted it before starting the backup. I see a 3.4TB "MacBook Pro di stefano.sparsebundle" file in the unit, and the control panel of the unit says "3.99TB free".

I would like to know if TimeMachine backups have a backup limit that I can remove somewhere so that I can complete the backup. I'm running macOS Sonoma 14.3.1.