My cycle computer has a table of numbers as yours does. The numbers are actually the supposed circumference of the wheel in millimeters. Simply measuring the wheel does not account for the slight change in diameter of the wheel that happens when your weight rests upon the seat. Make a mark on the sidewalk. Align your valve stem with this mark. With your weight bearing down on the bicycle, move it forward one complete rotation of the wheels. Mark the spot below the valve stem and measure back to the first mark. Convert the measurement to millimeters and that is the figure to use for your cycle computer.

I have two bicycles with identical cycle computers on them. I set both as described above. In a 14 mile ride there is still about a tenth of a mile difference between their readings, but either one of them can vary a tenth of a mile on different days. I do not know why. Maybe the reed switch tripped by the spoke magnet does not always respond the same at different speeds. If you need anything more accurate, you will probably need a Garmin tracking you by GPS.