Hello,
It is possible to use digital inputs for different purposes. Normally they are used to activate digital or analog outputs or certain types of actions. (reboot, activate wifi, send SMS or email). There is an option to run a script after receiving a digital input, you could make a script that adds to a variable after each activation and print the value by shell console. Then, you could check this value by logging into the router. Another option would be counting after posting text messages or emails after receiving the Digital Input.
Here is a link with more information about the actions and I/O pins of the RUT955.
https://wiki.teltonika-networks.com/view/RUT955_Input/Output
Regarding the odometer. The GPS function of the RUT955 can not measure kilometers traveled. Its function is mainly to identify where the device is located, and It does this by locating the coordinates of the device. They can be sent to a server or stored in the router. You can estimate kilometers traveled with these coordinates. However, for these more specific tracking functions, it is advisable to use the FMB130, since it has better integration with the vehicle's functionalities.
Likewise, here you have the information about the GPS functionalities of our RUT955.
https://wiki.teltonika-networks.com/view/RUT955_GPS