There are several apps & websites you can use to look at your usage. Personally I use Octopus Compare on my phone, which allows for custom tariff settings. Not sure if it works with IO though, I've never checked. It will definitely show your 30-minute usage if not the actual cost breakdown.Thanks. Would be good if you could produce one yourself for recent days.
Edit: Just checked the app, it does indeed support Intelligent Octopus in the list of tariffs.