I downloaded the Intervals.icu app earlier this week, and have noticed that the training zone is one level different than it is in the browser-based program.
Yesterday my training zone was gray zone in the browser, but optimal in the app. Today, I’m optimal in the browser, but high risk in the app.
For today both browser and app show Fitness - 44, Fatigure - 60. The browser-based program calculates the form as - 16 (Optimal), and the App puts me at -36% (High Risk)