I don't understand why I have a half-cast?

[lizziewhiz]

I fell down the stairs on Wednesday (today is Friday), and I hurt my foot. I went to A&E where they X-Rayed my foot. The doctor said there was no fracture that showed up on the X-Ray, but he said it was possible that I did have one. He said he would give me a half-cast, and I've got one, it's just I don't understand whether I will have a full cast at the end of the week. The Doctor didn't say - so for a possible (unknown) fracture, do you think I'll get a full cast? Thank you!