The Fontself Maker extension exports fonts only as OpenType files (.OTF).

If you need web font files (WOFF, WOFF2), TrueType (.TTF), .EOT or .SVG files, other tools are needed. Just be aware that many font conversion tools do not yet support color fonts nor bitmap fonts.

You can try using: http://www.fontsquirrel.com/tools/webfont-generator

To generate a TTF file, just click on Expert... & select TrueType in Font Formats.