In this case you must consider two effects: the action of the force and the effect of the weight of the object:
\(F_T = m\cdot a\ \to\ f + p = m\cdot a\ \to\ a = \frac{f + (m\cdot g)}{m}\)
\(a = \frac{68,6\ N + (7\ kg\cdot 9,8\ m/s^2)}{7\ kg} = \frac{137,2\ N}{7\ kg} = \bf 19,6\frac{m}{s^2}\)
