Jera has everything to do with perfect time; 'whay you sow, you shall reap'.
The rune implies that the user has an understanding of the mysteries of time, and the psychological effect of dividing & managing time.
Jera can speed things up, and can also slow things down in accordance with what has been sown. If someone were to plant no seeds, and have no desire or intention in their thoughts, then Jera would reap an outcome that would reflect this lack of action.