need help to correct the humidity %

[ambersandboa17]

i have few groups from Facebook, there handful groups give me some not very clean what correct humidity %..

some of them say 30-40%..

some of them say 40-50%..

some zilla bag (bedding) say 50%-60%..

even google not give me exacity anwers.

even the sandboa book not tell what exacity % for my sandboa. Because i first timer own sandboa, and i am still learning how to take care my sandboa.. i only own him for about 6 month.

here my tank look like.. and there say 41% humidity.

i need to understand about humidity, because i kind of little confused lol

thank you so much!!!!