Lowballed myself during interview, now they’re trying to offer me less than job ad. How to proceed?

Essentially the title.

I may have lowballed myself saying I wanted $20-21 per hour for a position I recently applied for. I know it was a mistake, but I’ve been out of work for a couple months and was staring to get worried. I just got the offer letter today and they’re offering me $20 per hour. However, after the interview I reread the job description and noticed that it explicitly states “the starting salary for this position is $22 per hour.”

Would it be okay to bring this up in an email to the hiring manager? Or do I risk losing the job? How should I proceed?

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