Cap-height not exporting correctly with variable font

I am designing a variable dot-matrix font. But on export it displays the CAP-height as the top of the letterform rather than how it is in Glyphs. See screen grabs attached for context.

Hope you can help.

What do you mean, on export? Are you opening the exported .ttf/.otf in Glyphs again?

No Sorry I wasn’t very clear. The first screen grab is using the fonts in Adobe. The bottom grab is in Glyphs. I’d like the cap height to reflect how it is in Glyphs. However when I export the font and install it, it seems to register the top of the letterform as the Cap height

The cap height is not a metric exported in the font metadata. InDesign (or other Adobe apps) will guess the intended cap height based on your design. I don’t know what is generally used by which software to calculate the cap height, but I would guess the capital H. What does that look like in your font, does it align with the cap height?

I would otherwise point you to this very comprehensive tutorial: Vertical metrics | Glyphs

Adobe uses the hight of the lowercase “d” to determine the position of the first baseline in a text frame. You need to add a tiny shape at the cap hight of the “d” to “fix” this.

Amazing, thank you.