I cut mine 1/4 deep or 1/3 the board thickness, believe me it's enough oncce nailed/screwed.
Another point I can't stress is useing a scrap piece of melamine to do test cuts. This will ensure you are geting the correct depth, as well as width. I know the board says 3/4" but sometimes they are a little this way or that. something to think about. With Dado's you don't want them to tight or loose, thats the hard part but with patience and a scrap board you will be fine.
Another tip do all the same width and depth first. You want to adjust the blade or bit as little as possible to ensure uniformity. I use two differnt size dado's this may not be true in your case.
Take your time and be patient, it will turn out, and at the very least you will learn better for next time.
Good Luck
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Jeremy
"I am become death, the destroyer of worlds" July 16, 1945 Robert Oppenheimer
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