this setting will basically send a 250w to the Trainer. (You can create a workout w/ a range, but trainers will not be able to interpret it as a range, it needs an actual number - so it will use 250w)
if you’re in ERG mode, that is basically what you will be doing.
What you want to do for 240-260w range would be to use the trainer in SIM/SLOPE mode where it’s like you’re outdoors and you use your gears to control your effort.
in Zwift - i believe it’s called FreeRide mode. (not exactly sure)
If you’re on iOS, you can give my BreakAway: Indoor Training App a test. You can send the SLOPE/SIM mode and switch between ERG and SLOPE (use your gears) at will