10 gal batch frequency

If you look just above that paragraph to the last one it talks about it a little more:

"You can also use a method called "capping" where you add extra malts to the mash after you have run off the big beer, to add more character or create a completely different wort. Try making an all Marris Otter English Barleywine, and after running off the BW wort, add a 1/2 pound of crystal malt and roast barley along with 1 pound of chocolate malt to make a stout, or maybe 1 pound crystal and 1/2# chocolate for a brown. You could even add 1/2 pound of Carafa III to that all Pils base mentioned above for a Schwarbier."​

The capping grains reference in the 3rd paragraph is waiting to get the grains to infuse their color, flavor, body, sugars, etc into the existing mash. Just mix them into the mash after you have already pulled the first runnings beer, let them steep and convert (make sure your mash never gets above 158 if you are planning to add new base malt), then sparge and run off the second beer.