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://offer.ebay.com/ws/eBayISAPI.dll?RetractBidShow
