Battery starts empty charge at 70% & case doesn't drain below 5%

When I try to calibrate my AirPods battery, it goes down to zero then I put them back into the case. However, the app reports the charge being at 70-80 percent even though it has been around 8 seconds. Also, I am trying to drain the case down below 5 percent but I am unable to. Are both of these actions normal behavior for AirPods because my AirPods 2 are able start battery charging at zero percent and charge normally.