array question

{=AVERAGE(IF(($J$12:$J$10786>R1)*($J$12:$J$10786<=R2),$S$12:$S$10786))}

In the above, column J is a column of values
R1 - R5 is a list of values in numerical order 150, 300, 800, 5000 etc.
Column S contains percentages

The formula displays the average percentage of all values in column J that are
greater than R1 AND less than or equal R2.

Can someone explain why the formula works by multiplying the ranges?

thanks

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