The SM-MA-F203P/PM adapter that you bought is a 23mm adapter for using a 203mm rotor with 180mm post mounts
The SM-MA-F203P/P adapter is a 43mm adapter that lets you use a 203mm rotor with a 160mm post mounts.
The SRAM 40mm Post adapter lets you use a 200mm rotor with 160mm post mounts.
43mm:
https://www.jensonusa.com/Shimano-F2...-Brake-Adapter
40mm:
https://www.bikeman.com/BR2041.html