After a bit of reading it’s looking like the issue is using the phone for a hotspot.  Apparently this requires more data than just using one’s phone.  Well, learn something every day.

Speed test can TEAR through data.

If your speed is 100Mbps, speed test usually lasts for about 20 seconds or so.

100Mbps * 20 seconds = 2000Mb used

2000Mb / 8 = 250MB used

So even with only a 100Mbps speed, you’ll use about 250MB of data just in the speed test alone.

You ran “couple of speed tests”? Well sir, that’s your issue there. 

The amount a speediest uses highly depends on your Internet speed. In general, the up and down tests are each run for 15 seconds as fast as it can, or until it down/uploaded 300 MB.

So, assuming you have a symmetrical 100 Mbps line, the speedtest would use 15s * 100 Mbps = 1500 Mbit = 187.5 MB in each direction. That’s how you used most of it I suppose.

EDIT : Delete please.

Thanks, folks.  I truly had no idea.

To add, tablets have much more screen real estate than your typical smartphone. This means that displaying content on your tablet will often use more data. Smartphone screens are smaller and specifically designed for mobile internet usage. Most phones can autodetect screen resolutions because many sites are mobile-friendly.

Mobile-friendly sites usually begin with an ‘m’ (e.g. m.youtube.com). When accessing the same site with your tablet, you may have accessed the desktop version of the site (e.g. https://www.youtube.com).

The desktop version of the site may not detect your device’s resolution automatically. Or your device may settle on the highest (or lowest) resolution possible, which in turn, uses more data due to the amount of additional information displayed on the screen, versus the mobile-friendly version. If the video had options for 2K or 4K resolution, you would notice a significant increase in data usage.

I tried this again last night without doing speedtests (derp), and watched an animated 22 minutes show in 480p on my tablet through hotspot.  Barely a scratch in my data.