I'm working with LM324 to learn how to use Op-Amp and all aspects of it. currently my circuit is this(a simple non-inverting Amp):

And here is a table of inputs and outputs and the gain of each input:

The gain of each input is odd to me. I'm trying to increase the accuracy of this circuit as possible as. I have applied 9.6mv in the input and got 4.75v in the output. or for 11.2mv I got 5.39v. What's the problem? IIRC the max input offset voltage is 7mv. Am I right? please show me by mathematical calculation that why the output is this? the gain isn't correct. should I bias the input offset current or offset voltage? How?