guessing font width

[bill lam <cbill lam gmail com>]

I use gnumeric on debian and I use dejavu sans mono, but each time
gnumeric started opening excel files will give a warning

** (gnumeric:11164): WARNING **: EXCEL : unknown widths for font
'DejaVu Sans Mono', guessing

the width it guessed seemed smaller than actual and it made column
width that based on this font be narrower than it should be.  Why does
it need to guess when that dejavu  font has been installed in system?
(I can choose the font within gnumeric's font dialog box).

gnumeric version '1.9.4'

thanks in advances.

-- 
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