Well, that's just simple math.
Your weekly benefit is 1/2 of your average weekly earnings. That is, they add up your total for the two highest quarters, divide that by 26 and there's your weekly average. They divide that by 2 to get your UI benefit amount. So, figure: 2 x 26 x 601 = $31,256. So, the requirement to make $30,000 during your base period is really moot, because you have to have made more than that during your two highest quarters to max out anyway.
If you made $18,000 for the whole year, the highest weekly you can get is $346 (assuming you made it all in your two high quarters). If that is max, it isn't such a great max. You could theoretically get more from Mass. without maxing out. In fact, if you made the same $18,000 but filed in Mass., you would get the same $346 - but you would get it for four more weeks every year than in PA.