Increment amount not working properly?

Hi, first of all thank you for this beautiful plugins. Love it!

I want to ask question about inremental amount for bid. Please have a look:

(1) The product startinr price is 5000
(2) Minimum increment amount is 100

In my understanding, the bidder should enter price like: 5100, 5200, 5300 etc. But in my site, the first bidder can enter 5001 as the bid price, and succeed.

The next bidder (2nd bidder and so on) must enter 5001 or higher for the price bid.

Is it normal, that the first bidder can enter whatever number as bid price (like 5001 on example above?

Thank you,

Syauqe