Latest software update?

I'm usually a bit slow at doing software updates on my iPhone so currently it's on iOS 10.3.3. Last week I noticed it had downloaded iOS 11.0.3 and expected that to be replaced soon with 11.1.1 but today I checked under software update and it was telling me the only available update to be installed was iOS 11. I deleted the update and checked again but it's still saying the only available one I can download is iOS 11. Why would it have gone backwards and overwritten the later update with an earlier one? My iPad (also on 10.3.3) seems to have done the same thing, strangely.