The four dials, or clocks, are located on the HOS Screen in the driver app. These dials represent how many hours remain in a driver's Break, Drive, Shift and Cycle clocks.
The top left clock shows the time remaining in a driver’s shift until their 30 minute break.
The top right clock shows the drive time remaining in a driver’s shift until they are required to take a 10 hour break.
The bottom left clock represents how many hours of On Duty time a driver has before they must take a 10 hour break. Commonly referred to as a daily limit.
The bottom right clocks shows the time remaining on a driver’s cycle. This typically represents a 7/8 day or weekly limit.
You can view a brief summary of HOS regulations directly from the FMCSA here.