the other person has bid higher and it increments by 1 credits up to 200 and then 2 credits at a time. At 300 it is 3 credits at a time, 400 4 credits at a time up to 1000 where it is 50 credits, etc. Hope this helps. You just have to find out how much they bid by increasing your bid until you outbid them. Then it is up to them or anyone else to outbid you.
jherington - My bid is higher than your bids, so like blingsupreme said, it'll automatically keep raising the minimum bid until one of the two competing bids has been exceeded.