I do not use screen time any longer. It just was not useful for me. 
You should not trust this feature too much. Those numbers are indicators for her usage, but they can be misinterpreted or even flawed to some degree.
And many more - look for screen time in this community.
Regarding the grey bars or app usage not adding up:
So, tapping on “Show categories” and drilling down from there should provide more detailed information.
But do not trust Apple’s screen time too much. It might be better to somehow get back to a point where your daughter understands what is good for her and what not and to trust each other and to talk to each other about it. Please do not misunderstand me, I do not want to sound rude or anything and I know that this is not easy or possible in every situation.