Sleep paralysis episodes does count towards your sleeping hours and if you manage to sleep through it without waking up, you’d be none the wiser, in terms of sleep hours. You may recall the experience if it was severe, or have no recall of it at all. You would not have lost sleep.
Sleep is lost due to waking up during an episode. This was particularly difficult for me – being constantly woken up during deep or REM sleep. Going for significant periods of time without it caused sleep-related health problems.