Is it considered wrong to think that Dhikr is only with the tongue, and to intend to limit the reward to the number rather than to the heart and contemplation?

When remembering Allah, a Muslim should be mindful of His greatness and ponder the meanings [of the dhikr]. The best dhikr is that in which the heart and tongue are in harmony. If the heart is absent and the dhikr is confined to the tongue, there is still good and reward in it, although it is of a lesser degree. It is not a condition to simultaneously ponder Allah's creation during dhikr; such contemplation is desirable in itself. Dhikr with the tongue alone accustoms the tongue to remembrance, keeps it away from falsehood, wards off heedlessness, and expels Satan. Therefore, dhikr with the presence of heart and mind is superior, but if the heart is heedless, good still exists, though one must be wary of the whispers of Satan.