To use the grid to find your ride level, look at your recent rides to see your pace and determine the feet per mile for each ride. If you don’t have that history, record your average pace on your next few rides, figure out the feet/mile of each ride, and look across that row of the grid to find the average pace at which you finished the ride. Scan up the column where that pace is found to get the class of that ride.  If you don’t keep that data, ask one of the people you typically ride with.  You’ll find that almost all your rides will fall into just one or two levels.  When deciding if you belong on a ride, look at the targeted pace and the feet per mile (or figure it out) and you’ll know if it’s in your class.