It's actually a bit different than what you'd get from that table. NL (like most countries) has varying population density. What's not obvious is that NL has a crazy distribution where we have a large chunk (the 'Randstad') that contains a very large portion of the population and a relatively much larger area that is just about empty.

So depending on where you are you can travel for 150 Km and never leave the built-up areas or you can travel for 150 Km and you'll see nothing but grass, cows, the occasional farm and the highway you're on (A6/A7).