Memory usage related to your account quota is distinct from the memory used on the clusters to process jobs.
Your account at Galaxy Main https://usegalaxy.org is well under quota (250 GB) and it looks as if you already know how to permanently delete (purge) to recover space. FAQs for others reading: https://galaxyproject.org/support/#account
I didn't find any failed Freebayes jobs in that same account. I do see some successful runs from yesterday. Jobs can error with a memory failure for a variety of reasons, generally related to input format problems but sometimes due to the use of parameter settings that create a very large job or the data actually being too large to process. These FAQs explain how to troubleshoot and then (if needed) report problems that you cannot solve when working at Galaxy Main or can reproduce the error there: https://galaxyproject.org/support/#unexpected-results
Thanks! Jen, Galaxy team