iTunes and updating songs I've not listened to

Hello, I'm new here, so forgive me for using this as a support desk. I promise I have looked this up, but can't find anything that helps me.

Whenever I plug my iPod Classic into my iTunes (running on MBA Mid-2011) to put new music on it, it will update songs that I've not played since the last update. All software is kept up to date.

Eg. I may only want to add a ten song album, but it will update say 100 songs. It's done this for a long time, is there something I can do to stop this? What's going on?

I hope someone can advise me on this.

Thanks in advance..