In reply to keith-ratcliffe:
If you stretch a modern 60cm sling between your thumbs, it is 60cm between your thumbs.
A bit of confusion for us oldies, is that in days gone by, we would have used 5 foot of tape to make a four foot sling, allowing 12 " for the knot.
still a single sling and about the same length.
hope that all makes sense.