Great that you have a plan and on track.
The 7.3% is basically 4^(1/20) calculation. Its the 20 year quadrupling percentage, with compounding.
I'm 80:20 ...global equity trackers to equity managed funds. Obviously excluding cash.
I never intend to sell, only drawdown but it will be a long time before that starts. I guess when you get to 10m usd why bother investing!