On the context, "sleep debt" seems to be from experiments at 4-5h per night restriction cumulated for many days [0]
How much sleep is actually needed above that will heavily depend on the person and what they do
[0] "Dinges, D.F. et al. (1997) Cumulative sleepiness, mood distur-
bance, and psychomotor vigilance performance decrements
during a week of sleep restricted to 4-5 hours per night." mentionned in the research article references
How much sleep is actually needed above that will heavily depend on the person and what they do
[0] "Dinges, D.F. et al. (1997) Cumulative sleepiness, mood distur- bance, and psychomotor vigilance performance decrements during a week of sleep restricted to 4-5 hours per night." mentionned in the research article references