How far the paper has stretched, or shrunk where it is negative, since
it was perforated, as a share of its length then: the strain
ΔL / L. It is a ratio of two lengths and so has no unit of its own,
and it is stated in per cent because what paper does is a matter of
tenths of one. It is taken in one direction, along the roll or across
it, since machine-made paper does not stretch the same way in both.
The standard uncertainty of the value, one standard deviation.
Left out where the measurement gave none, which leaves it no more
precise than paper is known to vary.
How far the paper has stretched, or shrunk where it is negative, since it was perforated, as a share of its length then: the strain ΔL / L. It is a ratio of two lengths and so has no unit of its own, and it is stated in per cent because what paper does is a matter of tenths of one. It is taken in one direction, along the roll or across it, since machine-made paper does not stretch the same way in both.
See
crm:E54 Dimension