Ijust looked up the instruction for seat height, basically, the heightshould be set where baby can touch the bottom with a flat foot using astraight leg. For more info, see page 19 of the instruction booklet.
http://www.gracobaby.com/assets/pdfs/instructions/ISPE020AA.pdf page 19.
沒說清楚,我記得會站之前應該是可以踮腳站,不過不能讓他自己支撐自己。