I don't understand how charges are allocated betwen order and activities

Hello,
After many tests, I don't understand anymore how are charges allocated to a project

I create a simple project, without any charges in the Project screen.
I create an order attached to this project, with 5 days of charges and an amount of 5000 € : theses charges and amount correctly appears on the project view 'Validated charges", and "validated costs"

After that, I create a activity, attached to this project, but first without any charge......and what's happend ? In the project view, the precedent charges (and amount) validated disappears
If I suppress this activity, the charges and amount don't appears anymore.....exept if I modify the order attached (amount or charge) : in this case, the project view will display again the charges and amount . (a right modification is necessary. a simple "save" without any modifications doesn't work)

Another test : If this time I create the same activity as before, attached to the same project, but with charges and amount this time. In this case, the project view display also only the charge and amount from this activity but dont make sum of charge from order and from activity (the same for amount)

And last test : in this situation (describe just before), I modify again my order (charge or amount, it is the same resultat), the project view display only the data from order and suppress informations from activity

It is as if the project take in account only the last input and supress the precedent.

Is it normal ? If yes, can someone explain me where I must input charge and amount ? I'm realy lost

Thanks

Edit 21h15
After other tests, my conclusion (but is it right ?) : we can't use order an activities together : if we use activities for input charges and amount, and only activities, all is fine. But if we affect an order, all the data coming from acivities are erased in the project screen and replace by the order(s)

That's right ?

Default value is "Consolidate only if set"
As you described your case, it seems youare in case "always consolidate"

Exactly. I changed the value to "Consolidate only if set" : I think it is the right value for waht I want to do.

But I don't realy understand the difference between "Consolidate only if set" and "Never consolidated".
In the "Never consolidated". state, what happend if activity has zeron value ? Not the same as for "Consolidate only if set" ?