SUPPORT REQUIRED PLEASE

SALAM, I want to modify the software for data communication, we have a Siemens PLC with S7-400 controlling a Fuel Treatment Plant. The Tank Level is coming real value i.e. if the actual level is 5.7 the reading is displayed as 6 meters however if the level is 5.3 the displayed value is 5 meters, No decimal values are considered. I need to modify the software to include the decimal value (2 digits). Can you help me in this and can I connect to the PLC through the ethernet cable, knowing that I'm new in using the S7 program.