In ‘My Order History’, what is the meaning of ‘Actual Rate’?  Also, how is ‘Costs / Proceeds’ field computed?

As I understand it (or so I thought), 'Actual Rate' is the actual rate I paid instead of what I bid and ‘Costs / Proceeds’ = ‘Actual Rate’ x ‘Units Filled’

However, it seems that currently it computes ‘Costs / Proceeds’ = ‘Bid/Ask’ x ‘Units Filled’

If Bittrex keeps the difference, this feels a bit scammy..

Is this normal for exchanges, can someone clarify this. Thanks.