Part of the reason AGO is running as it is, is because of the...

Part of the reason AGO is running as it is, is because of the type of base it has come off. The high of 108 and the low of 75.5 forms the last leg of the base. When price breaks above the high of that last leg it is classified as an extension (mostly from Fibonacci terminology). The target area of 200% is 200% of 108 to 75 from the leg low. 108 - 75 = 33 x2 = 66.

75+66 = 141.

The structure is important because it is recognised in so many various techniques all with similar methods of calculating target areas. It isn't complicated which is a big part of why it is so effective.