I was looking through the wiki and I came across the page for Avengers volume 6. I thought it was odd that this contained a single number 0 issue. I was wondering why this was considered a full volume and not just the 0-issue for the volume that is currently listed as "volume 7".
One-shots are always considered full volumes and it's not part of the subsequent volume because they were published years apart. (Avengers Vol 6 #0 was part of 2015's All-New, All-Different Marvel publishing initiative; meanwhile, the current volume, which began in 2017, is part of the Marvel NOW! publishing initiative.)