You will need to know what speed your wifi device is capable of to start with.....is it a 1x1, 2x2, 3x3 or 4x4 device?
1x1 has max 433 Mbps, 2x2 has max 866 Mbps, 3x3 has max 1300 Mbps & 4x4 has max 1732 Mbps.
You will get roughly 60% of rated wifi speed, as roughly 40% is wifi overhead, so that then gives you roughly:
1x1 device - 260 Mbps in perfect conditions
2x2 device - 520 Mbps in perfect conditions
3x3 device - 780 Mpbs in perfect conditions
4x4 device - 1040 Mbps in perfect conditions
Very, very few 4x4 devices.
A link or links to the source of your information would be handy
It’s on the Ubiquiti site, can not find the link at the moment.