How to tighten a Fox Thru Axle, Cam Lever/QR Skewer?
If you have a Fox QR15 thru axle (sounds like it), the only thing that's supposed to be adjustable is the rotational position of the axle nut in its splines, which if needed is done by loosening the 2.5mm bolt that keeps the axle nut keeper in place and sliding the keeper out of the way. To fasten down the axle, you thread it in much like threading a normal QR skewer in the QR nut, stopping when the lever begins to require force when it's about halfway through its travel, or parallel with the axle. You adjust the axle nut's position to make sure the lever ends up positioned how you want it when fastened and all the way down, i.e. tucked neatly in front of the fork leg.