Greetings Tinker Hydro ...
first things first ...
if you're using an RTD - and the input to the card is 4 to 20 mA - then that implies that you have some sort of transmitter located between the RTD and the PLC input module ... is that correct? ...
and if you have such a transmitter, have you checked the calibration on it? ... zero/span, etc.? ...
next item ... you really need to tell us the exact catalog number of the PLC input module that you're using ... that information definitely could affect the final answer to your question ... better yet, if you're allowed to post it, showing us the entire RSS program file will cut down on the amount of back-and-forth questions and answers like these ... check first ... some companies have strict "proprietary" and "trade secret" rules about their programs ...
also ... checking the calibration at one point only (example: 86 degs C) isn't usually going to give you enough data to do any sort of accurate calibration ... for most systems you need to check at least 5 points - and make a chart of the "expected" readings and the "actual" readings at each point ...
and welcome to the forum ...