Well, it calls for 1.5 quarts of peppers (before chopping) so that would equal 6 cups. Do you have a big measuring cup (I have one that's 8 cups) or anything that will measure a quart or more? Since it's a "yada yada" recipe anyway, stuff some in whatever measuring device you can muster and give it a try. What's also "pretty close" is one of those 1/4 peck bags that you buy apples in. A 1/4 peck is 2 quarts by dry volume, so fill it 3/4 full.

No seal of approval intended or implied :-)

That's 100% vinegar plus lemon juice, and 6 cups peppers when chopped won't yield that great an amount, so between the acid and the cooking (which will acidify everything), I doubt there's an issue anyway.

If I were making that recipe I'd measure then weigh the peppers for accuracy and consistency in future.

Carol