Opamp input bias current and current sources
The two input bias currents are not equal to each other.

The data sheet input bias current specification is actually the average of the two input bias currents.

The input offset current specification is the difference between the two input bias currents.

Input bias currents can flow into or out of  the opamp's inputs depending on type of input transistor. NPN transistor bias current flows in whereas for PNP input transistors bias current flows out.