RDX 1 TB Tapes only Holding 250G Before Overwriting

We used to have 250G RDX Tapes. We changed over to 1 TB drives so that we can hold 3 backups on each one before overwriting. The backup continues to overwrite after every backup instead of appending.

We have a media set with an overwrite protection set to 8 hours, append set to infinite.

The job is setup to append, overwrite if no media available.

The backup job is a little over 250G now, but 3 should still fit on one 1 TB tape.

I have tried searching for an answer and talking to a Symantec tech, but I have not gotten anywhere with it.

Thanks for any help!