Your instance was created this year, if that's what you mean. My instance is a year older:

Also, defederation would impact this as well. For all I know the missing posts are on lemmy.grad (for example).

Edit: actually it's definitely the age of your instance.

I got curious and decided to view my profile from feddit.org and it shows less than half of my total posts/comments

I like this actually, I look a little more well-adjusted lol. It also shows just how much effort I was putting into commenting on things early on to break the seal