I made a mistake on a bid, How do I correct it?

[hdr2fish]

Bid way too much- I am still in the lead, but I want to lower my Max bid.

[lady_madonna]

@hdr2fish 

You cannot lower your maximum proxy bid.

[woodland_gnome]

A typo in entering the bid amount is the ONLY bidder error that may be corrected by retracting the bid. You must rebid the correct amount (the amount you intended to type in the first place) immediately after the retraction goes through. There are time limits (12 hours before the scheduled auction end or 1 hour after the bid was placed, whichever is later, but in no case later than the actual end of the auction) so don't delay.
https://www.ebay.com/bfl/retractbid

For some other "mistake" in the bid amount you'd need to beg the seller to cancel it.