The mathematical model created actually works all the way down to 1 minute, but it's very hard for traders without enough experience to make consistent profits off of timeframes lower than 4H. 

But for everyone that's just starting out, experienced or not, we still recommend you trade on 1D timeframe to prevent the chances of making any emotional mistakes at the start. We do not recommend you to trade on 4H timeframe until you have mastered our strategy and become profitable with the daily timeframe.

Trading on a daily timeframe is a lot safer. The win probability for 4H timeframe is lower than daily because it requires more time on the screen to check the chart (basically every 4 hours).