correct.
6 total is the usual for issuing DAS, but the CMs in Guest Relations can make exceptions.
Depending on the attraction, there might be limits on the number the DAS Return Time can be issued for (but usually won’t).
If you need to use a special boarding area, the number allowed into the special boarding area may be limited.
For example, Toy Story Mania has a wheelchair accessible boarding area that guests get directed to at the Fastpass merge. The wheelchair accessible ride car that loads there only holds 6, so no more than 6 guests in a group are sent yo that boarding area. Some others (like Small World and the boat ride in Mexico) can hold 6 guests plus a wheelchair.
Others, like Splash Mountain, have small handicapped waiting areas for accessible boarding.
And shows may limit the number accompaning a guest who needs accessible seated because the amount of seats in the area is limited.