Is merely uttering a remembrance (dhikr), such as "La ilaha illa Allah wahdahu la sharika lah, lahul mulku wa lahul hamd, wa huwa 'ala kulli shay'in qadir" a hundred times, sufficient to attain the mentioned reward, or is it a condition to ponder and reflect upon its meaning? And is the same true for other forms of remembrance?

There are three levels of remembrance [dhikr (definition)]: the remembrance of the heart and tongue, which is the most virtuous; then the remembrance of the heart alone; and finally, the remembrance of the tongue alone. The latter still carries reward, habituates the tongue to it, keeps it from falsehood, repels Satan, and banishes heedlessness. The remembrance of the tongue alone is better than silence or backbiting. It is sunnah (definition) to strive for the presence of the heart and to reflect upon the remembrance.