Growatt 12k wire gauge confusion.

[Rosstafarian]

Good afternoon.
Manual recommends I use #6awg wire for 80amp breaker to the inverter. According to US standards the minimum wire to use for an 80amp breaker is #3awg. Looking at the terminal block on the Growatt and there is no way a #3 will fit into it. I know I saw someone on here “pair” down the wire and then heatshrink it to fit the remaining wire into the terminal. Kind of like taking a 6 lane highway and reducing it down to a 2 lane at the exit?
Thoughts?
Thank you.

 

[Cheap 4-life]

4 gauge wire is commonly used for service wires for homes that have a 100amp main breaker