I get that you messed up your sb when starting the auction. But if you fix it that way, the first bidder is forced to bid at 8 instead of the actual sb. Tbh, you should just restart an auction when you make a mistake like that.
Especially when it's in the rules that you can "Only bid on your own auction when cross posting on other sites"
Fixing a sb by bidding on it yourself doesn't really count as crossposting bids