Rhino
I take it you mean the weather settings numbers, heavy black italics on the left of Weather ribbon.  Tooltip is immediately to their left.
These allow you to set different views of the weather gribs you have downloaded.  So my #1 shows only wind and MSLP, #3 shows only currents, and so on.
You set up what shows under these number buttons by highlighting one, then going to Settings and recolouring the variables on the RHS, the grey area showing the wealther variables starting with MSLP.
Cheers.

Duncan is right. I can add that the e button is an ensemble display mode. So if you have multiple models or ensemble runs loaded, each will be shown in different colours.