VarData for VarSolid in COLRv1 format

[glukfonts]

hi,
I'm try to convert my variable, color font to COLRv1 format with ttx

As far my attempts were successful except variable gradients (PaintVarLinearGradient). Each use ends with empty, transparent layer in Chrome v.95.0.4638.54 ( PaintLinearGradient work good). I began to suspect that PaintVarLinearGradient and PaintVarSolid are not yet implemented in Chrome (btw. anyone can confirm this?)

to understand the idea of VarData I started with the simplest VarSolid with variable Alpha in ttx format:

<COLR>...<BaseGlyphList> ...</BaseGlyphList>
  <LayerList>
   <Paint index="7" Format="10">
     <Paint Format="3">
       <PaletteIndex value="1"/>
       <Alpha value="0.8"/>
       <VarIndexBase value="0"/>
     </Paint>
     <Glyph value="o.col2"/>
   </Paint>
  </LayerList>
   
  <VarStore Format="1">
     <Format value="1"/>
     <VarRegionList>
        <Region index="0">
           <VarRegionAxis index="0">
              <StartCoord value="0.0"/>
              <PeakCoord value="1.0"/>
              <EndCoord value="1.0"/>
           </VarRegionAxis>
        </Region>
     </VarRegionList>
     
     <VarData index="0">
       <NumShorts value="0"/>
       <VarRegionIndex index="0" value="0"/>
       <Item index="0" value="[0.1]"/>
     </VarData>
  </VarStore>
  
 </COLR>

and I got error from ttx:

TypeError: ('integer argument expected, got float', 0, 'Item[]', 0, 'VarData[]', 'VarStore')

And here is my question - alpha value is float 0.0-1.0, how delta for alpha could be integer? or my understanding for VarData is bad?