That recipe suffers from the same problem that many recipes suffer from that you find on the internet. Here, add this much fruit and this much sugar and you have the sugar level at the proper level. In any recipe I find, I check two things minimum, often three. Add 1/2 Sugar suggested, measure SG then add more sugar if required. Add 1/2 the Acid called for then measure the Ph and most times the TA of the mixture. Add more if required.
Oh and fruit, almost always double or triple and add less water than is called for, oftentimes none.