Before you choose in the conflict window
When: The Cloud Sync Conflict window is on screen
Don't click either option yet. Write down the dates and times shown for the local and cloud files.
Copy
Steam\userdata\<your Steam ID>\<app ID>\and the game's own save folder to another location as a safety backup. This is our own precaution; Valve's article only tells you to compare the dates.Pick the side whose timestamp matches your last real play session. If you're unsure, back up first and decide by your in-game progress.