IMHO that data is probably a maximum value...since VSF maximum throughput strictly depends (and varies with) the number (and type) of VSF logical port's physical members interfaces that are aggregable together to form the VSF logical port (forming a "load-balanced aggregate VSF connection with redundancy").
AFAIK the Aruba 2930F supports up to four (4) 10G physical interfaces (ports) for VSF logical port...and can use up to two (2) VSF logical ports (called simply VSF ports)...so the 80G limit is the maximum in a 2 VSF logical ports configuration made using 4+4 10Gbps interfaces.
Using specifically 1G physical interfaces (a scenario not permitted on Aruba 5400R zl2 VSF implementation) will let you - if I've read it correctly - to aggregate (to bind) up to 8 1G physical interfaces per VSF logical port (so a grandtotal of 8+8 1G - so a maximum of 16Gbps VSF throughput - considering you can deploy up to 2 VSF logical ports).
In Aruba 5400R zl2 with v3 zl2 Modules the (2 members) VSF can be deployed using single (or aggregated) 10G and 40G physical interfaces only...not 1G (and in a either/or implementation, not mixed)...so it boils down to the number of 10G or 40G ports you're going to reserve for each VSF logical port.
If my algebra is still OK and rules above are valid...on the Aruba 5400R zl2 you can deploy up to 8 40G physical interfaces per VSF logical port, up to two VSF logical ports as in Aruba 2930F? NO...as of today I think that Ring topology (so 2 VSF logical ports on the same VSF Member) is not permitted on Aruba 5400R zl2...it supports only VSF in Chain topology...so we go back to the 8 40G physical interfaces per one VSF logical port case on each VSF Member...this means a theoretical 320Gbps VSF throughput between the two Aruba 5400R zl2 VSF Members when using up to 8 40G ports...or just a theoretical 80G VSF throughput when using up to 8 10G ports to form the single VSF logical port as is actually permitted (not considering the potential oversubscriptions behind the corner and/or the 80Gbps bandwidth limit per slot on V3 zl2 Modules when the Aruba 5400R zl2 works in "v3 only mode").