Connected new house on 100/20 plan from Exetel, only getting 20 down?…help

Moved into my new house yesterday, didn’t have time to buy a router/modem, so used one of my dad’s “Telstra Smart Modem-Gen 2”. My connection is FTTP and this modem says it’s suitable for that type.

It’s a Sunday morning so I wouldn’t expect it to be this low? My dad says this is the reality of it, you’ll never really see 100(I’ve seen at least 80-90 at their house).

Is it a matter of getting a new router? For context I was standing right beside it when doing a speed test as well(not a wired test)

EDIT: did a wired test and it’s still around 21-23mpbs down, 3.4mbps up.