I don't think is HY, but you should be familiar with it. It shouldn't be confusing, it's actually very straight forward.
Just remember the basic rule when approaching any diagram, LOOK AT THE AXIS. In the Davenport, X axis is the pH, Y is the HCO3 and the CURVE LINES are the PCO2.
My approach to any pH imbalance:
First determine how is the pH (acidosis or alkalosis), then see if there's any respiratory or metabolic contribution (is the PCO2 high or low?, is the HCO3 high or low?); now put the "first name" (respiratory or metabolic) by determining whether PCO2 or HCO3 is causing the corresponding pH. Finally see if there's any compensation.