Dear respected Linda Jelsma,
Good day! Thank you for posting to Microsoft Community. We are happy to help you.
I’m sorry you’re having a problem but based on your description we can work together to resolve it.
For the situation you encountered, we deeply understand the inconvenience caused and apologize for it.
As per your description, yes, the formula you provided is supported in Microsoft Lists.
If Column A is a Choice field, the comparison might not work as expected if the choice includes spaces or is case-sensitive. Double-check that the value "Yes" matches exactly.
I tried in another way:
=IF(AND([Column A]="Yes", ISNUMBER([Column B])), [Column B] - 16, "")
If you need to use a comma (,) as a separator in your SharePoint calculated column formula instead of a semicolon (). In some regional settings, SharePoint uses a semicolon (;) as a delimiter for arguments in formulas.
Since you have the error in your list, I also suspect the problem is related to the language of the SharePoint site, the site collection administrator can check the original language of the site, and you can also check if the SharePoint multilingual feature is enabled? If yes, turn it off. Create multilingual SharePoint sites, pages, and news - Microsoft Support
In the meantime, could you please test in another SharePoint listing and check the result with us, please understand that it will help us to narrow down your problem.
Please understand that our initial reply may not always immediately resolve the issue. However, with your help and more detailed information, we can work together to find a solution.
I'm sorry and I apologize for that.
Appreciate your patience and understanding and thank you for your time and cooperation.
Sincerely,
Waqas Muhammad