I might not understand the whole problem, but I think it comes from your own coding experience with other programming language.

ProBuilder coding language has no array for personal variable (not yet but will come soon), and I think that you want your code to use it. A number in brackets [10] is just an offset of bars quantity on the chart, not the 10th value in an variable array.

“once” instruction is used to give a variable a value only one time at the first read of the code.

Have in mind, that ProScreener has a data history available of “only” 254 periods, so some discrepancies might occur between a chart and what ProScreener can read. ZigZag of 4 percent from peak to valley start at first bar available in history, and if the history is different, therefore the result can be different.