I agree with some of these other fellas but I would try it a different way.
1:Back off your magnetic controls all the way.
2:Pick out a lure or casting plug or jig or socket or nuts or something that weighs about 1/2 ounce.
3:hold the rod at a 45 degree angle... somewhere about 10-2
4: adjust the spool tension knob until the lure falls as fast as it can and touch the floor with out causing an over run.
5: once that is adjusted turn your magnetics up to about 90%.
6: make short easy casts and try to feel the lure(weight) load up the rod tip
7: once you've got this down, start backing the magnetics off.
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If you still get backlashes this way, try to tighten the spool (with the magnetics off) a little more to where you have to jiggle the lure to drop.

Biggest thing to remember is that you need to adjust it this way when changing different weighted lures and when different conditions present themselves IE.......@#!&*!$!.....WIND!!!!