Issues with a rebuilt 360

I have an msd distributor intial timing is pretty easy but I’m not sure about the Total timing I was told it’s where your timing is when your at about 3000 rpms but what I don’t get is how do you adjust total timing without touching initial timing if your adjusting both through the distributor
Do
Don’t understand 292 cam but I have a 540/560/326 duration flat tappet cam 750 quick fuel by Holley 4 corner idle tacked vacuum advance in distributor run 20 degrees on crank 18 degrees degrees of mechanical advance in distributor works and runs fine burns tires no prob. Can smash it to floor at any rpm and it just lights up. Also in a 360