Well, it's kind of important. If you want to know when the ban is over, you need to know what caused the ban and when. For example, it could be a 10-year 9B unlawful presence ban for accruing more than 1 year of unlawful presence and then leaving the US, but if she had an approved provisional unlawful presence waiver, then that ban should be waived, so unless she had another ban, she shouldn't have been denied. Was it a 10-year 9A ban for having been removed? Or maybe you are describing the lifetime 9C ban for which I-212 can only be filed after 10 years? Was it a 10-year ban for prostitution? I can't think of any other 10-year bans.