Percent uncertainty confusion

Question

Here is a problem where you have to calculate percent uncertainty for an angle and its sinus function. It calculates the uncertainty for its angle using the well known formula, then calculates uncertainty for sinus by subtracting maximum and minimum mistake uncertainties to get absolute uncertainty and divides it with its measured value. I understood this problem but then the problem beneath confused me:

In this problem the extreme volumes were subtracted but then divided by 2. Why is it divided by 2 in this problem but wasn't in the previous one? Can someone explain this please?