Equal !
(50%)

but if I go on ressource affectation, I can see all of affectation, at the end of the allocation table of the resource, I have the total of affectation rate... and it is an addition of the rates of the projects and sub-projects
If my ressource is affect at 50% on project and 50% also on the sub-project , the general rate is 100% ... it's not true.

Affectation rates do not add.
They are just constraints applied at each project level.

I did an example in attachement file:

this ressource is affect on 16-CAN-0424 (project) 100%
and 16-CAN-0424-01 (sub-project) 100%
and 16-CAN-0424-06 (sub-project) 100%

total is 300% and not 100%

is it correct ?

Yes, but this does not mean resource will work 3 days per day.
Just that resource is able to work on 100% on 3 different projects, but won't be planned 3 days per day.
Project priorities and dependencies will define on wich project resouce will work first.

so the 300% is not true, isn't it ?

Wes, it may be worng.
In fact is does not represent a value that will "overload" the ressource.
It is just a reminder of how "often" (on how many projects) same resource is allocated.