Bundle question - newish seller

I've never sold a bundle before, and I already have a 15% discount for 3 or more items on my shop. So is the buyer who is putting 4 items into a bundle looking for another/bigger discount? Or are they just gathering things they like? Is it considered expected-polite to toss a little extra discount towards the bundle?

As a buyer I wouldn't expect it if I'm already getting 15% off. But I have no idea how people think anymore.

I'm probably overthinking it....