??? if you mean ‘storage’ level then that is the voltage that you can safely store cells for a long period of time, many months even years, in cool dry conditions
Normally accepted by all manufacturers as 3.8v per cell for Li-Po or Li-Ion chemistries
HTH
Steve 
You could light a fire with a Samsung Note 7, banned by all airlines.
Yes of course I did mean storage level. A blip in my typing. What I want to understand is, what percentage of charge do you keep the batteries at? Do you keep charging to maximum and let them discharge naturally or keep them charged above a certain level. This being the case if not being used for a long period.
50% is a safe bet 
depends if you charged it to fly then didn’t, dischsrge to cell voltage 3.8v
If below 3.8v then charge upto that.
Basically do whatever you need until all cells are about 3.8v.
I always do 3.7v. 20% capacity I think
My new Q8 stores at 3.8. used.to do 3.75… don’t keep em high if been charged and not been used.