So my supervisor offered me the permanent position. The downfall of it is that it on for a…

So my supervisor offered me the permanent position. The downfall of it is that it on for a guaranteed 20 hrs a week. But she said can schedule me for 40 hrs. It pays $4 more than get now. I just hope I get the 40 hours otherwise I would be getting less even though I make more. She said that I move up to full time when a position comes available. I get benefits and vacation time, 401k and pension.