No they have got it all wrong. The buttock line is the crease that is left in the sofa after you have sat on it for too long. The length of the buttock line divided by the softness factor of the sofa will give you the arse size.
Sometimes you get multiple buttock lines this is caused by figiting. If you divide the number of lines by the time spent on the sofa then sub divide by the arse size and multiply buy the sofa softnes factor you will get the wobbly bot index.
Hope this has been of help
