Mittens are charted in 56 and 68-st wide.
Use sport-weight yarn for 56st. version, or fingering-weight for wider version. By sport-weight, I mean 6-ply sock yarns like Regia or Opal or similar. Whatever label says, Teksrena and similar yarns with 350 m/100 g knit more like fingering-weight.
Miminal duplicate stitch embroidery required (see a few white stitches on birds wings and eyes).
The charts are, as always, in full color, but you can easily use less colors.
35 X 35 = 10 cm
300 yards of Fingering weight