ESP32 LOW SPEED RPM TACHOMETER

I need RPM_Measure.ino modified so it will show RPM in the 10-40 RPM range with a sensor going HIGH on each revolution (IR sensor). RPM_Measure.ino is an example code of the https://github.com/khoih-prog/ESP32TimerInterrupt library. RPM_Measure.ino is at
https://github.com/khoih-prog/ESP32TimerInterrupt/tree/master/examples/RPM_Measure
I am running code on Arduino IDE on an ESP32-WROOM-DA