Cffridcolumn numberformat comma issue

Hi,

I'm using cfgrid cfgridcolumn to display data on a page.  Somehow the following code does not show the comma.  Cfgrid is in html format.

<cfgridcolumnname="InletFlueGasFlow_acfm"numberformat="9,999,999"header="Inlet Flue Gas Flow ACFM">

tried also with type

<cfgridcolumnname="InletFlueGasFlow_acfm"  type="numeric" numberformat="9,999,999"header="Inlet Flue Gas Flow ACFM">

What is a valid numberformat?  The Adobe documentation for cfgridcolumn says numberformat="format"

9 Optional digit placeholder. Same as _ but shows decimal places more clearly.

, Separates thousands with commas.

Any idea why my comma not showing?

Thanks.