Sweet little garment for colder days. Modified the collar (many more stitches, details see below).

Body needle size 6.00 mm
Side and hem ribbings needle size 5.5 mm

Ribbing: Round edge + 8 rows

Added 5 cm length to the body
Start decreasing after 7th bar row, on row 3 of the pattern.

Front and back: 114 gr
Side ribbing: 36 gr
Collar: 30 gr

Picked up 48 and 49 stitches for the side ribbing (uneven number in order to start and end with a knit stitch)

Collar knit as described in the pattern resulted in a very narrow neck opening, no chance to get it over the head.

Re-did the collar: pick-up 2, cast-on 1 all around, ribbing with needle size 6 mm

Tubular cast on as shown by Ysolda
Tubular bind-off of the collar as shown by very pink