It means it's almost all VG (vegetable glycerin). The 2 main components of
eliquid are propolyene glycol (PG) and VG. VG is thick, sweeter, and produces more, vapor. PG is thinner, provides better throat hit and reportedly provides more flavor.
When using clearomizers, I wouldn't go higher than a 70% VG
juice. I've found 50/50 to be my preferred ratio. Flow is a consideration with
eliquid. Since VG is thick, high VG juice may cause wicking issues and lead to a burnt taste and possibly reduced coil life. Generally, max VG juice is used in RDAS (drippers) and RTAs (rebuildable tank atomizers).
Some people may have an allergy to PG and thus use max VG.
It's a personal preference aside from the flow and allergy considerations.