That is a bug in Photoshop where it deletes the presets. I recommend backing up the presets after you recreate them. Under the manage presets section there is an option to export and import presets.
When you create a preset, there is an option to resample which is off be default. If it is off then the final image size is just the actual amount of pixels left over after cropping. If you turn it on then the image will resize to that exact amount. So for example, if you have the preset set at 8×10, 300 PPI then you will get 2400 x 3000 pixels. Keep in mind that upsizing will typically results in blurred pixels. So for example, if you have it set to crop tight around the face then you may not have very many pixels left over after cropping since most of the image is being cropped off. Say for example there are only 1500 pixel in height left over after cropping and you force it to 3000 then you are upsizing by 200%.
In any case, just turn on the resampling and do the math you need. The actual number of pixels will be the inch dimensions multiplied by the PPI you set in the preset.