ERA5 Pressure Values on Theta Levels

How do I interpret the Pressure values in this dataset? I downloaded ERA5 Potential Vorticity and Pressure(Monthly means of Daily means, analysis, Potential Temperature levels) . The pressure data doesn’t make sence to me. Please see the attached image. The potential vorticity data makes sense. It is a 2D grid with the same shape as the lats/lons. But the pressure data is 1D with a length that doesn’t match anything I can think of. Any advice? Thanks!