What does Clean Base Rotation mean and how is it defined?

[GaominZ]

as the title, what is clean base rotation defined and mean?

for example, it says 2025/05/06 18:32:06 

which tables' data will be cleaned up at the time? " Log Entry[syslog]"??
Or the one oldest so far, which is "Log Entry [syslog0007]??

I have already read the document and still have the question. please kindly explain to me. 
Apply table rotation

[GaominZ]

here is a capture more clear