The first of two screens for logging a strength set: dial in the weight you're actually using before moving on to reps.
The number starts on your prescribed working weight, in whichever unit (kg or lb) you display. Adjusting it takes effect immediately, so backing out to the set overview and returning later keeps whatever you'd already dialed in.

A weight that doesn't land exactly on your target — a machine pin, say — is completely normal; see "Why doesn't my logged weight match the target exactly?".
Related: "The reps screen on your watch", "Why doesn't my logged weight match the target exactly?", "Logging a workout".