Is 4.0 a good number for bone mass on a healthometer scale for a 51 year old woman?

I found a chart on the Senior Life Health web page. It uses weight and age as a self assessment tool. The chart is for postmenopausal women. A 50 - 54 yr old woman who weighs 154-164 and has a bone mass of 5, 4, 3, or 2 is in the low risk range for osteoperosis.

This is the link:

http://9www.seniorlifehealth.com/productcart/pc/viewPrd.asp?idproduct=10&idcategory=

Scroll down the page to see the chart. Part of it is cut off, but if you right click the chart and save it to your computer, you can get the whole chart.