Troubles with SIMS 4 Studio and HML file

[Trud]

Hello everyone. I'm new to this sort of thing, not just making mods ... but recently I tried to make a clip and package with 1 animation.
Here's what I experianced.

1. Regarding Sims 4 Studio:
I cannot change the the value of the Duration (Frame Count X Frame Duration) of Clip/Clip Header in Sims 4 Studio.
I calculated the exact value for my 1 animation, but whenever I tried write the new value and save the change -
Duration resorted to a default number!
I assure you: MY calculation is NOT what the the default Duration number is.
Has anyone experianced something like this - with S4 Studio or other programs?

2. Regarding XML file:
If I make a pack with 1 animation (1 actor), do I have to keep the section of the HML file about "Receiving Actor" (2-4 lines of the code)?
(whatever the type of interation)
Considering the actor's value is "0" since he is the first (and only) actor in the animation.

Any of these problems could be the reason I can't get my 1 animation to work. Also ... I'm terrible at programming!
Any help would be greatly appreciated.
Thank you all in advance!