Windows 10 has a basic data usage monitor built in, though as far as I can tell it will only give you information on the last 30 days, rather than any smaller intervals. Go to Settings, Network & Internet, Data usage. Then click on View usage per app.
You can get a basic idea if you do nothing Internet-related on your PC but your game. In "Network and Sharing Center", "Network Connections", double-click on your Ethernet/WiFi adapter. A status window will open, with current counters of transmitted and received bytes. Make a screenshot, play your game, make another screenshot, calculate.