Clue is the feedback R on the op amp. Notice each flip flop has different R values, and that affects the ratio with the feedback R. Eventually, after so many clock ticks, the op amp will "trigger" the OFF state when the op amp has the right value on the inverting input pin.
Since that diagram does not appear to show any signals to the J, K, PRE or CLR inputs, the circuit operation is not clearly defined.
You'd have to assume that all those inputs are high for the circuit to work.