The Stroudwater, and Thames and Severn for that matter, locks never had numbers just names were referenced that way in documents. Someone produced a basic map in the early 2000s for the website and copied the Huddersfield way of doing things with 6W, 10E, etc. which kind of made sense. I can't remember who originally produced the map referenced in the posts above which was adopted by the CCT but the numbers are just for clarity and the key gives the names of the locks. What really does grate with me with that map is that they've started the numbering of the locks from Stroud with the Thames and Severn numbered from west to east and the Stroudwater from east to west. The Stroudwater was constructed first and so if that numbering system was in use then, the first lock you got to off the Severn would have been lock 12 (if you counted each chamber of Ryeford Double as a lock on its own).