Gixen not bid the your bid but one more dollar of the last

[apektos1000]

What I mean with that is it will be better if you tell the bot that you paying 100 max for this item and in the in 2 seconds left someone bids 85 dollars, so the bot will bid 86 dollars and gets the item.
Something that is not happening and it's gonna bid 100 dollars so your profit will be lower.

[mario]

When Gixen places your maximum bid eBay proxy bidder takes over and you don't necessarily end up paying 100 - in such scenario you will win it for 85 + bid increment.

[Rickajho]

The exception to this rule - and possibly what the OP was referring to - is when an item has a Reserve Price set.

If the reserve price is $100.00 and the bidder before you bid $85.00 max then their bid goes to $85.00.

If you bid next and have gixen place a bid of $100.00 or more, and the reserve is $100.00, your bid automatically goes to meet the reserve price. The same thing would have happened if you placed that bid directly on an eBay site.

You cannot win this type of auction with a bid lower than the reserve price.

These are eBay bidding rules on items with a reserve price. Be mindful of eBay listings that have a reserve set.

Rick