LP8868X-Q1: R_LED value

Part Number: LP8868X-Q1

Tool/software:

I'm looking to use LP886X-Q1 to control multiple LEDs and am not sure how to find R_LED to be able to calculate other external component values.

It's deltaVf/deltaIf, but I don't know if deltaVf is the voltage across the LEDs or something else, and how I'd find deltaIf, or if it has to be retrieved from the LED's datasheet/info?

Thanks!