Sorry to make you wait so long for a reply, it took me a while to notice the alert.
On a 2-4 result, your attempt fails without adding a time penalty. There may be consequences, based on what you were trying to do. Eg, leaping between buildings - fail and you fall, and have to make at least one roll to save yourself. Or you land badly and gain a condition.
My interpretation of spending a banked success is that you can take one of the actions in the spending time section without adding any minutes to the timer.
