Re: SS Question?
Do the weight from Friday's workout. The biggest problem people run into with SS is they stall because they jump through the weight too quickly. The point of the program is PROGRESSIVE overload. You can't skip workouts/weights and expect the program to remain progressive.
EDIT: Looks like I misread the question. I would do the planned weight for Friday on Monday since you aren't "skipping" anything and you're still early in the program. However, note what I said above...try to avoid missing workouts, it's a surefire way to stall.