I'm not sure, i had this same question, and it doesn't make any logical sense because
A centimeter is a centimeter but in the video apparently not... for example in the video it showed the notebook as 40cm for one and the next one shows it as 14.4 cm it stayed as cm both times the size of the ruler should not change that one ruler was by 10cm the other was by 1 cm and it showed 2 completely different numbers
so therefore it doesn't make any logical sense
here was my measurements from the little video it had
try getting ahold of the teacher or whoever gave you the question its all you really can do...
hope this helped even tho it probably didn't