What is the meaning of "equal difference multiplied by equal ratio" in dislocation subtraction method

What is the meaning of "equal difference multiplied by equal ratio" in dislocation subtraction method

The equal ratio sequence multiplied by the common ratio q is Sn =
QSn=.
The first term of QSn corresponds to the second term of Sn, 1 to 2, 2 to 3
(1-Q)Sn=.
Divide 1-Q and you'll get it