Inaccurate Total Float Calcs

Newly created production scheduler position in fabrication. They had a basic schedule in Microsoft Project that I converted into P3. When I created the project I let it just default to the date P3 wanted in project overview as this project never ends (hopefully). I have all correct logic and durations. For some reason only a few of the activities in each job are picking up that default date of the project must finish by in project overview and giving me float of (example)1,956 hrs. when the rest show 20 hrs. I went to tools/schedule/options to check float calc and I changed it from critical to finish. F9 and still no change. I could understand it picking up that odd date it has no pred/succ. Only thing is that some are being worked out of sequence but I don’t remember having it effect before.

Any help is greatly appreciated! Beth