Starting this new thread, because the older one has been shut,

Looking in my linux distro, firefox and about:config something like the following appears

Code:

storage.vacuum.last.places.sqlite: 1474885593

When using bleachbit, this very file named places.sqlite I am told it can't be deleted. In my unix machine I just delete it. In both cases it is a user set integer. So someone can tell me if this is unix time, number of times for visits on certain urls with a maximum set?
Mozilla help tells me, this is about a database, telling all my hits and visits. Wiping it out in my BSD, all my bookmarks are gone, that does not bother me at all.
So does anyone has got a clue on this?

Thanks in advance