Hang about!
A 100% increase on £22k would give a new rent of £44k.
A 50% increase on £22k would give a new rent of £33k - an additional £11k. Without doing much maths, clearly the increase is a little lower than 50%.

What you have calculated is what fraction the old rent is of the new rent - 22/31 or 70%. If the rent was unchanged, then this figure would be 100%!

Calculators do not have much common sense at times.