See the question and my original answer on StackOverflow

DirectWrite simulates "oblique" fonts (that are not in the physical files).

For Oblique, the slant is achieved by performing a shear transformation on the characters from a normal font. When a true italic font is not available on a computer or printer, an oblique style can be generated from the normal font and used to simulate an italic font.

So you'll get 'Oblique', 'Narrow Oblique', 'Bold Oblique', 'Narrow Bold Oblique', 'Black Oblique' simulated fonts for a total of 14.

If italic is available, oblique should not be used.

You can check that using the IDWriteFontFace::GetSimulations method, on each font, which will get you back DWRITE_FONT_SIMULATIONS_OBLIQUE for those fonts.