I use keyboard shortcuts to navigate around Discourse sites including here on meta itself. The shortcut Goto New (g,n) shows me a few new posts whereas Goto Latest (g, l) shows me many many more including both after and before the most recent few visible from g, n. The same problem shows up with Goto Unread (g, u) and Goto Latest
Here are my meta preference settings.
Pretty much the default settings and none that suggest to me why Goto New and Goto Latest should give vastly different results as you can see here in screen shots taken while composing this post.