求翻译：（4）PVC地面卷材应在铺贴前3~6天进行裁切，并留有0.5%的余量，因为塑料在切割后有一定的收缩。是什么意思？

(4) PVC roll on the ground should be trimmed paving 3-6 days before, and will have a 0.5% cushion, because after the cutting, plastic has a certain amount of shrinkage.