What I was trying to say is the baby is growing faster. If you stay at average weight throughout your life, like you're tracking along the 50% line on the growt

What I was trying to say is the baby is growing faster. If you stay at average weight throughout your life, like you're tracking along the 50% line on the growth chart, then your fastest weight gain is in your first year. On average that's when you gain the most weight (even in absolute terms), despite the fact that you're much much smaller than, say, a growing teenager.