Technically, you can select any server you want. You are testing the connection from your router to the server through the internet naman eh.
Globe recommends their server because they are nearer and within the same network. Meaning, they can speed it up. I prefer using multiple servers within and outside the country for much more assurance.
Using your mobile phone, download and install Speedtest.net by Ookla.
After installing, run the app, click Begin Test and select the nearest server, preferably a Globe server