Ideally you would jack up rear, check wheels are not binding. TIghten the 10mm nut and keep rechecking that rear wheels are not binding with the handbrake off. If you over tighten the nut it causes the rear pads to bind. If it starts to bind, undo the 10mm nut to the point where rear wheels are free again - and thats the handbrake adjusted!
There is no way to individually adjust each side it is just a cable clipped into the caliper itself there are no handbrake shoes and there is no adjustment in the lever either - and since the left and right hand side share the same fulcrum point the only way to adjust the tension is the cables is to adjust the free play at the mechanism shown in this video… this is also as per the instructions from main dealer too 👍🏽 hope that helps
