so the store page mentions both 15 new levels and 43, so which is it? did they mean to say 15 chapters across 43 levels? should probably fix that!

that's a pretty big difference in number of levels for someone to decide if the price-point is worth it.

The DLC adds 15 new maps plus the Arrange Mode versions of the original 28 maps. Those add up to 43, so I guess that's what they're doing. :)