Good question. RMAN backup and recovery has its own forum, and not strictly related to XE either.
Short answer, It Depends. Depends on how the backups are run, how rman has been configured, what defaults are used and which defaults are overridden.
Others here might have better info than myself, don't get to use rman much. I can tell you that out-of-the-box with XE, using the db_backup_recovery_dest location for backup files, there is an (arbitrary) limit of 10GiB on space usage in the recovery destination location. Where it is, and what the limit is, those questions are easily answered using a system connection:
... password ... Connected.
show parameter db_reco
db_recovery_file_dest ... <path>
One caveat, if archivelog mode is enabled, and the archivelog location is not specified, the instance uses the reco...file_dest location for the archivelog files too. And if that file usage counts towards that default 10G limit, well, will have to depend on others here that will know that answer to that question, sorry