If the reserve price is higher or equal to the entered maximum auto-bid, your bid will automatically increase to the maximum auto-bid amount.
For example, say the starting price of a listing is $3,000 but the reserve price is $5,000 if somebody places an auto-bid of $5,000 then the system will automatically place this bid of $5,000 regardless of starting price. If somebody else then bids up to a maximum of $5,000, the 1st bidder auto-bid price of $5,000 will remain the highest bidder and the 2nd bidder is informed that they will need to increase their bid to at least $5,100 to outbid the 1st bidder. If nobody else bids, the 1st bidder will be successful as their bid matches the reserve price.
However if the starting price is $5,000 and the reserve is $10,000 if somebody places an auto-bid of $5,000 then the system will automatically enter their maximum bid of $5,000 because, although this may be lower than reserve, the buyer has indiciated their willingness to pay that amount for the listing. If no other bids are placed, the bidder will not be successful, even though they are the highest bidder, because their maximum auto-bid does not meet the reserve price.
Once the bidding has reached the reserve price, any further auto-bids will be placed in the noted incremental amounts. For example, if the reserve price is $10,000 and there is a current bid of $10,000 if somebody else places an auto-bid of $15,000 the system will place a bid of $10,100 for the listing on their behalf. The previous highest bidder will be notified that they have been outbid and will be required to place another bid higher than $15,000 (the 2nd bidder's highest auto-bid amount) in order to be successful.
If two bidders both enter an auto-bid amount that is higher than the reserve price, the system will automatically increase both bids to the point that one bid exceeds the other's maximum amount.