Yes it is that 22mm nut. Remove the rear seat and the LH seat panel. Loosen the 22mm top locknut under the seat after removing the split pin. You'll be able to jack it up slightly using a 22mm open ended spanner, but make sure you leave enough room to get the split pin back in.
Are you adjusting ride height because you're tall? If you raise the rear the bike will turn quicker, raise it too much it will get very twitchy. It also affect the swingarm angle which in turn affects bike handling.