Product Unit does not show "pieces"

[edudflog]

I am truly new to Virtuemart and have had several challenges.  I've worked through most on my own but this one has me stumped.

On the Product Dimensions and Weight tab in the product module, the Product Unit drop down list only shows the following:

kg, 100 mg, m, m², m³, l and 100ml.  It does not show "pieces" which is what I need.  How do I get "pieces" onto the list so it will display?

Thanks for anyone's assistance.

[edudflog]

Sorry - I forgot the following:

Joomla v 2.5.6
VM 2.0.10

Thanks

[edudflog]

Sorry - left off PHP ver: 5.2.17