subscript in index entry?

[Nancy Allison]

I need to create an index entry for an SF6 circuit breaker.

My webmail client doesn't allow me to put the 6 in a subscript, but 
that's where it should be.

I've tried this in the Marker box:

SF<Subscript>6<Default Paragraph Font>

The result is that both the 6 and the following page number are 
displayed as subscripts:

SF
    6 12

I tried adding an ending space and a semicolon as if another marker 
would follow:
SF<Subscript>6<Default Paragraph Font> ;

Same result. How do I tell Frame to apply the subscript only to the 6 
and not the page number in the index?

Thanks!