What materials are the interior walls made from? thats the key. 

Yes, they can cover that much area but under optimal conditions. A house made with brick/adobe/plaster lathe/etc are going to block wifi signals

So what are the optimal conditions? 

open spaces are ideal. 

The more walls/material in the way, the more the wifi gets blocked. 

It passes through sheetrock/wood better than the reset but that still attenuates the signal. 

This site has a few that show how much they attenuate but miss a lot like metal (hvac, foil lined insulation, etc)

https://wifivitae.com/2021/12/15/wall-attenuation/

Well according to your link you sent I shouldn't have a problem. Besides I had a Motorola gateway before I bought this one. It didn't have a problem with wifi signal. It was almost 10 years old 

What band are you testing on? 

What actual speeds do you get? 

what device are you testing with? 

did you try moving it laterally in case something in the walls is blocking? 

How many walls are between the 2 spaces? 

The technician from my internet provider came out and tested it and said the g34 is no good. He put the wifi tester on the machine and it lost half the signal when he moved the tester a foot away. So it's not where I put it or any interference.  My old modem worked fine. It was almost ten years old and works better than the g34