It is easy to understand, maybe you don't look at the colour alone on this in other not to get it wrong, in case it seems confusing to you, the best to do is by checking underneath and see the cost for each order of priority, they place the amount there, which you will see form the example illustrated by Charles-Tim, if you find the cost lower and affordable by you, then make the transaction, that is the essence of the mempool tracking, to know the cost before making a transaction, while the fee is assigned on each priority level.