Some warnings with PdfReader

[Vadkoz]

I need to get a count of the pages of the pdf file.
Got the next warnings when reading pdf via PdfReader or PdfFileReader:
Multiple definitions in dictionary at byte **** for key /Info
incorrect startxref pointer(some number (i got 1 and 3))

But I got a count of pages anyway, despite any warnings. I need to know if the count I got is correct. Maybe that warnings means something important that may interfere with the receipt of information, I don't know. So I checked several files, but I'm still not sure about it.
Thanks!

[MartinThoma]

Please see https://pypdf2.readthedocs.io/en/latest/user/robustness.html and https://pypdf2.readthedocs.io/en/latest/user/suppress-warnings.html