The book I have has a the number 33 written on the ISBN bar code on the inside front cover of the book. After reading the below guidelines, am I correct that it would be okay since it is not in the TEXT part of the book?

No writing or highlighting on text pages

• a signature or note on the flyleaf or inside front or back cover is OKAY
• an author's signature on the title page is OKAY
• writing or highlighting on the text pages is NOT OKAY
  • Exception: if it is a textbook or workbook, these are expected to have highlighting/writing
    • if you post a textbook/workbook, the condition must be described to the requestor in a Personal Message
    • AND the described condition MUST BE AGREED TO before the book is sent
    • This is the one of the ONLY two cases in which a PM exchange about a book is required before the book can be sent(the other is for cookbooks--see below).

should be fine if it is on the inside cover

Yep, you read that correctly