Ubiquiti UniFi Wi-Fi 6 Long-Range 4×4 MU-MIMO Access Point

It's difficult to give you an exact answer to this, as there are a lot of real-world factors at play that would affect the range (and, radius) that you're able to achieve out of this Ubiquiti UniFi6 Long-Range, which mostly depends on your surroundings, as well as the strength of the receiving antennas on the devices which you have connected to it.

However, in theory it should be possible to get a rough calculation on what to expect, and whilst it does include some complicated math, I'll link to article which helps make sense of these calculations and breaks it down quite nicely for you here: https://www.electronicdesign.com/technologies/communications/article/21796484/understanding-wireless-range-calculations

We'll use the following calculation:
Maximum path loss = transmit power – receiver sensitivity + gains – losses

Maximum path loss = 26dBm – (Based on your Receiving Device | Assuming -55dB) + (4dBi for 2.4GHz & 5.5dBi for 5GHz Transmitter | Assuming 6dBi Receiver) – (Based on your Environment - We'll Assume 12dB)

This gives us a Maximum Path Loss of 26 - (-55) + 10 (2.4GHz) / 11.5 (5GHz) - 12 = 79dB for 2.4GHz or 80.5dB for 5GHz.

Finally, we use the following formula to get an idea of roughly what range to expect:

Distance (km) = 10^{(maximum path loss – 32.44 – 20log(f))/20}

Where f is the frequency in MHz, which would equate to 2400MHz and 5000MHz respectively.

Therefore, for the 2.4GHz Frequency Range: Distance (km) = 10^{(79 – 32.44 – 67.60)/20} = 0.088715601204km (or ~88.7 meters)

And for the 5GHz Frequency Range, Distance (km) = 10^{(80.5 – 32.44 – 73.98)/20} = 0.0505824662km (or ~50.5 meters)

You could also additionally use an online calculator, such as this one: https://www.rapidtables.com/calc/math/Exponent_Calculator.html?x1=10&x2=-1.296
Just bear in mind that for a WiFi connection you would ideally like to aim for a signal of less than 60dB to keep a strong connection, as described in this article here: https://eyenetworks.no/en/wifi-signal-strength/

I hope you've found this information helpful!

** Please note though these calculations are not actual guaranteed values, and the results which you achieve will differ based on factors like environment, the strength of the receiving device's WiFi Antenna / Receiver & other factors as described in the articles above.