You need either 2 tabs open in your search browser or a secondary device to do this, on one tab click primary device, on the other you click secondary, type in the code you get into the secondary. start the test from the primary and you'll get the ping. Make sure turbo mode is on for both tabs (shift+green flag)
This program measures your ping from your device to the scratch servers with 1 decimal Make sure you enter the code before you start the test. You can retry the test as much as you want without clicking the green flag.