loft roll

Slightly random question! I'm adding 200mm loft insulation, Knauf 200mm Super Top Up Loft Roll Insulation https://www.wickes.co.uk/Knauf-200mm-Super-Top-Up-Loft-Roll-Insulation---5-61m2/p/109451 Obviously it's not 200mmm on the roll, but how long should I expect to wait for it to expand once...