Just assume that 87 is max vol and be done with it. On some Meridian products they can display 0 instead of 87 for 0db (reference) and show +/- db so you know that you are attenuating or amplifying.

Just think of it that Meridian volume can go all the way to 11 ! Actually 99 where 87 is full scale.

Worth pointing out that some Meridian systems can do 99 with ease and that 87 (0db) should equate to reference SPL of 75db.

Meridian owner since 1992
Prime & PSU, Focal Elear headphones, Roon (ROCK 8Gi5 NUC), Explorer 1 & 2, F80. 200/203, various Sonos (via Roon).