For this pattern, do the increase rounds with the M1P as indicated. On the next round, incorporate that increase into the Granite stitch pattern. You'll keep the pattern of ribbing the same (either a 2 or a 3 stitch rib) but increase the Granite stitch.
So for round 1 of the Granite, the repeat is k1, p3, then the increase stitch would be a k1 (your pattern would end: k1, p3, k1 before the marker) and so on until you have enough stitches for a full repeat of the pattern. Basically, keep increasing even though you won't have enough sts for a full pattern repeat.
Of course this is a little more complicated because the Granite stitch pattern changes from rows 1&2 to rows 3&4 but if you keep track of the row number you're on you should be ok.