110
hmmm... I get:
Table maintenance
* Check table Documentation
* Analyze table Documentation
* Repair table Documentation
* Optimize table Documentation
* Flush the table ("FLUSH") Documentation
may be your version of phpma, you can try optimize (if you see it (on the structure or options tab once you have sessions selected)) or just make sure no one is logged into the site and empty the sessions table (don't empty the _bb_ tables though... choose optimize for them)