minimize in metric pddl

Question

I created the pddl domain for the figure here

However, when trying to reach the node number 7 the output of the Metric-ff planner is cost = 21 insted of 15

also for the node 5 the cost = 16 insted of 10 it seems it minimizes the number of steps insted of the cost can some one help?

(define (problem petriproblem)
    (:domain petri)
    (:objects
        token - token
        spring summer fall winter - place
    )
    (:init

        (at token spring)
        (= (initial-token token) 3)
        (connected token spring summer)
        (connected token summer fall)
        (connected token fall winter)
        (connected token winter spring)
        (= (required-token spring summer) 1)
        (= (required-token summer fall) 1)
        (= (required-token fall winter) 1)
        (= (total-tokens-used) 0) )
    (:goal
            (at token winter)
    )
    (:metric minimize
        (total-tokens-used)
    )
)
------------------------------------------------------------------------
(define (problem nodes)
    (:domain petri)
    (:objects
        token - token
        node1 node2 node3 node4 node5 node6 node7 - place
    )
    (:init

        (at token node1)
        (= (initial-token token) 1000)
        (connected token node1 node2)
        (connected token node2 node4)
        (connected token node3 node5)
        (connected token node4 node3)
        (connected token node4 node5)
        (connected token node4 node6)
        (connected token node4 node7)
        (connected token node6 node7)
        (= (required-token node1 node2) 2)
        (= (required-token node2 node4) 4)
        (= (required-token node3 node5) 2)
        (= (required-token node4 node3) 2)
        (= (required-token node4 node5) 10)
        (= (required-token node4 node6) 4)
        (= (required-token node4 node7) 15)
        (= (required-token node6 node7) 5)
        (= (total-tokens-used) 0)

    )
    (:goal
        (at token node5)
    )
    (:metric minimize
        (total-tokens-used)
    )
)