Used user quota incredibly big ¿where to search?

Hi! I have several users, but one of them is growing too fast, but I cant find why.

In CWP -> User Quota, I get:

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*** Report for user quotas on device /dev/md2
Block grace time: 7days; Inode grace time: 7days
                        Space limits                File limits
User            used          soft          hard       grace    used  soft  hard  grace
theuser  +-  72114M  50000M  50000M     10:19    579k     0     0       

If I

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du -sch /home/theuser
I get:

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3,4G /home/theuser/
3,4G total
If I run a query to know database size, I get:

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theuser_db -- 13.45410156 MB
So, is there something I am not counting?

PS: I discovered there is a lot of space used in backups, but is it inside the user quota?