Don't know how that works but I use this site for the data. It might give you a much bigger area but it works pretty good.
SRTM Data Search
just select one of the squares then press 'begin search' then download the data from the links in the bottom.
Here is another tutorial for real life terrain, if you follow it just skip the first google step and get that data with the other link I provided.
https://www.realitymod.com/forum/f189-m ... heavy.html