Does the hadith: "Indeed, a servant may pray a prayer, and only half of it is recorded for him... Only what the servant comprehends of his prayer is recorded for him" mean that the prayer is never accepted in its entirety?

The aforementioned Hadith (definition) indicates that the completeness of the prayer's reward depends on the completeness of devotion (khushu') and presence of heart therein. Ammar ibn Yasir narrated this Hadith as evidence for his initiative against the devil's forgetfulness, emphasizing that prayer is not accepted as valid, nor is a reward recorded for it, unless it is performed fully with its limits and devotion. Any deficiency in devotion leads to a decrease in reward. Whoever observes all the limits of prayer and shows devotion in all its parts is hoped to receive the full reward. The proof for this is the Hadith of the Prophet, peace and blessings be upon him: "Indeed, a servant may perform a prayer, and nothing of it is recorded for him except a tenth, a ninth, an eighth, a seventh, a sixth, a fifth, a quarter, a third, or a half." This indicates the varying rewards for worshippers according to the degree of their hearts' presence and their devotion.