Font formats + kindle

Apologies if this question is in the wrong forum. I am using .otf fonts generated from Glyphs for use in an ebook, however the following warning notifications appear in Kindlegen about the font format

Info(prcgen):I1014: Converting and merging media file “/var/folders/8d/3162zh715pj3495b8x12395h0000gn/T/mobi-QaxysG/OEBPS/font/myfont.otf”

Warning(prcfile):W14029: CFF/Type1 (Postscript) embedded font included in your source may not render clearly on all Kindle readers. Please refer to Kindle Publishing Guidelines on the recommended usage of embedded fonts.

The relevant Publishing Guidelines state:

9.3.8 Using Embedded Fonts
Kindle Format 8 supports embedded fonts within the eBook. These fonts can be either Open Type (OTF) or True Type (TTF). Kindle does not recommend the use of Type 1 (Postscript) fonts. To provide Kindle customers with the best possible reading experience, reflowable books that use Type 1 fonts are rendered using Kindle fonts by default. On KF8-enabled devices and apps, customers have the option to turn publisher-provided fonts on or off.

The print edition acrobat file is seeing them as Type 1 also, but DTL OTMaster tells me they are OTF.
So I thought it was good with using OTF — any ideas why the fonts are being interpreted as Type 1?

They might refer to the outline format. Try to export as TrueType. It will export an OpenType font with TT outlines.