There are often discrepancies on how to measure a window and also how to measure the position of the window. This confusion usually result in a delays in production (proofs having to be made two or three times) or the envelope having to be re-done at the customer’s expense. That is why it is critical when a customer requests a custom envelope with a window to have a proof made to check the inserted document to the window position. The measuring of position and size is an industry standard.
An envelope is always measured with the flap at the top regardless if the flap is on the long side or the short side.
The window size is measured vertically first and horizontal second.
The position is always from the left and the bottom.