In the context of the linked source (in German "Die Feeding Rate sollte mit 105 % eingestellt werden"), with "a feeding rate of 105 %" is meant the extrusion multiplier (there is no reference in the source to Cura). This is explained in this answer. The answer is correct for the translation, but should have warned for the incorrect wording. Technically, feed rate is not a synonym for extrusion multiplier.
The source is wrongly using the term "feeding rate", feeding rate is the rate at which all steppers are scaled, not solely the E (extruder) stepper.
In G-code this is found to be the F
parameter, e.g. in G1 F1200 X76.468 Y148.947 E0.0264
the feed rate of 1200 mm/min is applied on all steppers, in this example X, Y and E. Changing the feed rate changes all speeds for all steppers simultaneously. This is found in G-code M220
.
The extrusion multiplier (or known as "Flow Percentage") only acts on the E stepper motor, this is not reflected in the G-code, but adjusted in the firmware planner. The G-code to adjust the flow percentage is M221