I had a BMW Cruise Control (on a bike - but I believe the cars were the same).
When switching it on a light came on - on the dash.
I then had the option of 'SETting' it to the speed I was doing or 'RESuming' the speed I had previously set.
Once under way I could adjust the cruise speed up or down in 1 mph increments.
Touching the brakes, clutch or closing the throttle disengaged it.
Turning off the ignition removed the settings.
I wouldn't work below 30mph or above 100mph (on a 155mph bike . . spoilsports

).
From the legends on the stalk it looks as though the Toyota system is similar.
Try it out - but don't accidently 'RESume' an 85mph cruising speed in a 40 limit
Bob.