I recently received 50 rep, though having a look at where it might have come from, I have no idea.

I am a member of multiple sites, and there is no indication of where the rep might have come from. The amount seemed slightly unusual too; 50 rep with no explanation. I know in some cases rep can be "re-awarded" from downvoted answers that have been deleted, but 50 rep seems way too high for this too be the case. Can anyone else clarify what this might have come from?
EDIT: It's happened again.

As we can see, another unexplained 50 rep has appeared on my profile. I had a bit of a poke around, and this time it seems to have appeared on my Scifi & Fantasy profile, but once again, it is completely unexplained.
Does anyone know what causes this?
