In the flow meter configuration software you can see a section with flow rate thresholds:

Direct and Delta flow meters detect current operation mode based on these thresholds
Current mode  is applied till instant fuel consumption (per hour) still lower than threshold (subtractive consumption for Delta).

For example for this values

3 Liters per hour - Idle
10 Liters per hour - Nominal
40 Liters per hour - Nominal
55 Liters per hour - Overload
105 Liters per hour - Someone cheating flow meter