Alignment Zones in exported fonts

I’ve set the Family Alignment Zones to match the Regular weight Alignment Zones.
On export and looking at the font file in OTMA both the BlueValues/OtherBlues and FamilyBlues/FamilyOtherBlues are different. Notably the values in the OtherBlues and FamilyOtherBlues. I was expeting them to be identical in the Regular font.

This is exported from Glyphs 2. A quick test from Glyphs 3 had the same result.

I remain confused as to how Glyphs handles the Alignment Zones and Family Alignment Zones.

How does Glyphs (2 and 3) differentiate between BlueValues and OtherBlues?
If I have a Bottom Zone (OtherBlue) that is above the Baseline (such as bottom alignment zone of superiors) – how is this specified so Glyphs knows it is a bottom zone? Is it dependent on specifiying the top or bottom of the zone and a pos or neg range?

In the Glyphs Manual you state that only 5 top zones and 6 bottom zones can be specified. Whereas the spec says up to 7 top pairs and up to 5 bottom pairs.

I guess I could just ignore Glyphs and edit in OTMA but this seems a bit painful (perhaps).

same font exported from FontLab 7 - and its results in OTMA

Thank you for the nudge. I had another look at the spec. I refer to ‘Type1 Font Format’ published by Adobe. Chapter 5.3 BlueValues, page 36 and 37, my emphasis:

And then there is chapter 5.4 OtherBlues, page 38, again my emphasis:

So, in the wording of the spec, it is one ‘baseline overshoot’, six ‘top-zones’ and five bottom-zones. So, if you count the baseline overshoot as a bottom zone (which is how it is treated in the Glyphs UI), it is six and six. This is how I described it in the tutorial:

And: It does not matter whether OtherBlues are above or below the baseline, the spec specifically lists the superior baseline overshoot in the examples for OtherBlues. I remember a misleading blogpost on Adobe’s blog stating that OtherBlues were meant for metrics below the baseline. But that makes no sense.

The new PDF manual is in the works, but will still take a while. Tutorials currently take precedence. I hope to find more time in the Xmas holidays.

and for the link – I couldn’t find that as I was searching for ‘Alignment Zones’

I was beginning to guess that Baseline was treated as a Bottom Zone . . .
All sorted now :+1:t2: