JustLimit monitors your mobile-data allowance locally on your iPhone and can block cellular traffic once your safe stop target is reached.
Why does the app ask for a VPN profile? JustLimit uses a local Network Extension so it can block cellular traffic. No traffic passes through JustLimit servers.
Does the measurement match my carrier exactly? Not exactly. iOS counters and route changes can lag, which is why JustLimit keeps a safety reserve. Always compare with your carrier's figures.
Where is my data stored? On your device only. Hourly totals are kept for at most 62 days and can be erased in Settings.