What constitutes "logs"? 1st. time buyer.

I am investigating the purchase of an a/c. The "logs" are looseleaf
sheets in a binder. When people speak of a log I envision a journal
with sequentially numbered pages. Entries are made in the pages and
there is backup substantiation in the form of invoices, yellow tags,
etc. Should I be troubled by the "logs" being tendered or is this a
normal situation.

Any guidance in this matter would be much appreciated.

Thanks,

Paul