Well what happens in Australia when CASA the ruling authority do a Safety Audit on a Company. They collect the following documents and check for correlation of figures.
1. Pilot Log Book
2. Flight and Duty Times
3.Aircraft Tech log and /or Maitenance Release
If they find a discrepancy, they give you the right of reply to explain. But if it unexpalainable, and theres a trend of it. The Non-compliance is reported and has to be corrected.
It is also a Federal Offence in Australia, and most ICAO nations to tamper or miss log hours with intent.
The catch is they have to prove intent, if you have a valid argumanent and it was an oversite on your behave, you may get the benefit of the doubt.
A Log Book is your personal record, but infact is the property of the ruling authority if under investigation. So keep it straight as it is an injustice to yourself if you tamper with it.
Also prospective employers, will eventually find out your real experience level, if yuove given yourself a Biro Boost so to speak.
Regards
SHEEP