technical problem

Hello;

I have two problems:

1) For "heat transfer module" time-dependent :
We consider a concrete slab :
- The lower surface at T = 293.15 K set
- The face higher flow q = 200W / m ^ 2
how to represent a heating time of 30 min and a cooling time of 180 min in COMSOL

2) I don't understand what does mean the flow q=360*(t<=900s)