The axis values in fontmanifest.json files are using the output rather than input axis values from the designspace.
Each <instance> in the designspace has an xvalue for each axis that specifies where it is in the design ("output") coordinate space. However the axis location in the font - and in the fontmanifest.json file must be converted to the user ("input") coordinate space value by looking it up in <axes><axis><map>.
The axis values in fontmanifest.json files are using the output rather than input axis values from the designspace.
Each
<instance>in the designspace has anxvaluefor each axis that specifies where it is in the design ("output") coordinate space. However the axis location in the font - and in thefontmanifest.jsonfile must be converted to the user ("input") coordinate space value by looking it up in<axes><axis><map>.