Terms

First Crack:At approximately 196 °C (385 °F), the coffee will emit an audible cracking sound. This point is referred to as "first crack", marking the beginnings of a "light roast". At first crack, a large amount of the coffee's moisture has been evaporated and the beans will increase in size.
FC = ((-TRT × DTR) + TRT)

Total Roast Time:The amount of time passed from the start of the roast to the point where the roast is finished by removing the coffee beans from the roaster and cooled.
TRT = (FC ÷ (1 - DTR))

Development Time:The period after the start of first crack until the end of the roast. Getting the development right will mean your coffee will have balanced acidity, with excellent body and sweetness.
Dev. Time = (TRT - FC)

Development Time Ratio:DTR is calculated as time from First Crack to the end of the roast, as a percentage of total roast time.
DTR = ((Dev. Time) ÷ (TRT))

Error Codes

div/0:Divide by zero!!! This error code signals that when calculating the DTR... a value of '00:00' was entered for the TRT.

fc>tt:FIRST CRACK TIME is greater than the TOTAL ROAST TIME. Since the first crack happens during the roast... This is not possible.