Hello Chris
The offset is the difference between the local clock and the master clock. This value remains the same regardless of what the propagation delay is. If the offset were to be calculated at 11 seconds, then at the time of synchronization, the synchronization process would subtract 11 seconds from the clock of the slave. If you go through the process you will realize that this would give us an incorrect result.
So you see, the offset and the delay are two independent values that are unrelated as far as the synchronization goes, so you wouldn’t add them together. To make this clearer, imagine that the delay was 5 seconds. Doing the calculations and the process that Rene goes through in the Clock Synchronization section of the lesson with 5 seconds instead, you’ll see that the result is the same.
I hope this has been helpful!
Laz