Well sadly the is a lot of "expert" on youtube and a lot things we have to correct the probe should NEVER be inside the enclosure regarding of the type of enclosure it should be sandwich between the uth and the bottom of the tank so on the OUTSIDE. Once done you simply adjust your t-stat to whatever setting allows you to achieve optimal temperatures.
Now why is that? Well it simple probe placed inside can
Be dislodged
Be cooled down if the animal pees large amount and they will
Be cooled down if the water dish is tipped over which they will do too
All of which will result in a false reading, leading the t-stat to think the temps are not where they should be, which means there will be an increase in heat which can and will lead to thermal burns.
There is obviously no one fit all set up it depends on the enclosure thickness and type, UTH, T-stat etc you just want to play with it (preferably without the animal inside which is why we recommend to setup an enclosure prior to acquiring an animal) so you achieve a stable desired temps anywhere between 88 and 90