It appears that you have a secondary axis system in the chart, which means that one or more data series must be assigned to the secondary axis system. When you have a secondary axis system, Excel orders things in the legend according to axis system first, then series order.

It is difficult to tell from a picture, but I would guess that your "max rate" series is assigned to the secondary axis, and that is why it shows up later in the legend. I would expect to go through each series and more carefully decide which series to assign to the primary and which series to assign to the secondary axes.