iCloud sync
From the app’s English Help & Guide · Reference release 1.0.19
Overview
Your Metered data syncs between your own devices via your personal iCloud account. Enable or disable it in More › Data. Apple handles iCloud transport and storage; Cocoacorn does not run a Metered server and cannot read your iCloud data.
Health data is different: Metered reads it from Apple Health on the device where permission was granted, and Metered does not write that health data into iCloud.