If your list has many formulas, the Status Bar might show "Filter Mode"
instead of a count of the visible records. You can use the Subtotal
function to count the visible rows.

The Status Bar may also show 'Filter Mode' if a cell in the list is
changed, after a filter has been applied.

The following MSKB article has information:

XL2000: Excel AutoFilter Status Bar Message Shows "Filter Mode"
       http://support.microsoft.com/default.aspx?id=213886

And there are a couple of workarounds here:
       http://www.contextures.com/xlautofilter02.html#Count