The Current High Bidder - 

May add, increase, decrease, or remove their maximum bid amount 
anytime during the course of the auction while they maintain the
highest bidder status.  The basic intention of this option is to
allow highest bidder the ablity to change the max bid without 
bidding against themself.   
This is not intented to increase the max bid amounts have already 
been exceeded, in that situation a new bid should be submitted.

To use this feature enter an bid amount equal (or higher) to your
current bid and the new max amount.  This will not increase your
previous bid unless you have intentionally entered a higher bid nor 
will it consider your previous max.