Charge cycle
One full cycle equals using 100% of the battery, in one go or in pieces. Two 50% charges add up to one cycle; it's not 'every time you plug in'.
A charge cycle isn't every time you plug the car in. It's the sum of energy equal to one full charge. If you use 50% one day and another 50% the next, together they count as one cycle, not two.
That's why charging little and often doesn't punish the battery: what counts is the total energy that flowed through it, not how many times you plugged in. It's one of the two clocks of aging.