What does it mean that the manas internally grasps the ālayavijñāna as self?

This means that the manas grasps the functions and operations of the ālayavijñāna as its own functions and operations, without knowing that these are the functions and operations of the ālayavijñāna. Following along with the dharmas that the ālayavijñāna perceives, it takes these dharmas to be "me" and "mine," not knowing that they are produced by the ālayavijñāna, belong to the ālayavijñāna, and are in essence all of the nature of the ālayavijñāna. Therefore it craves and clings to the functions and operations of the ālayavijñāna, delights in the functions and operations of the ālayavijñāna, and grasps at the functions and operations of the ālayavijñāna. Because of these graspings and craving attachments, the manas is bound, unable to attain liberation, and thus there is birth and death that it cannot relinquish or escape. The manas fundamentally does not recognize what dharma the ālayavijñāna is; so it is not that it grasps at the ālayavijñāna itself, but rather it mistakenly takes all the functions produced by the ālayavijñāna as its own functions, and takes all dharmas as belonging to itself, thereby giving rise to grasping.

What are the functions and operations of the ālayavijñāna? Nothing other than the functions and operations of the five aggregates and eighteen realms in their operation, nothing other than the functions and operations of all worldly dharmas. The manas takes these functions and operations as "me" and "mine." This misunderstanding only begins to be gradually dissolved after one realizes the ālayavijñāna. When the manas realizes the ālayavijñāna, it will, together with the mind consciousness, observe that the functions and operations of the five aggregates and eighteen realms are all produced by the ālayavijñāna, are the functions and operations of the ālayavijñāna, and are not the functions of the manas, of "me." Thereupon, the grasping at self is gradually eliminated. Then, as one successively realizes that all other dharmas are also the functions and operations of the ālayavijñāna, and not the functions of the manas, of "me," the grasping at dharmas is gradually eliminated, ignorance is gradually exhausted, one accomplishes the unsurpassed nirvāṇa, and attains great liberation.

Animals all have grasping at self and grasping at dharmas—which of them can know that there is an ālayavijñāna? They merely take those functions produced by the ālayavijñāna, those dharmas that are born forth, as their own. What the manas grasps at is only those dharmas produced by the ālayavijñāna—how could it be grasping at the ālayavijñāna itself?

Studying the Dharma is not about dissecting words; one cannot go around in circles on the literal surface of the text. One must deeply engage in contemplative practice (vipaśyanā-caryā) on its profound meaning and ultimate meaning. Most people's study of the Dharma consists of very shallow deliberation (manana) by the consciousness; they never cultivate meditative concentration (samādhi) to think deeply and contemplate. That is why so many people cultivate and study the Small Vehicle's teachings on suffering, emptiness, impermanence, and non-self, yet in the end arrive at the conclusion that "the five aggregates are not the eighth consciousness and are not different from the eighth consciousness"—a conclusion that is logically incoherent. What ordinary being would ever hold the notion that the five aggregates are the eighth consciousness? Anyone who holds this notion would no longer be an ordinary being, and would not need to engage in contemplative practice to eliminate self-view (ātma-dṛṣṭi) or to personally realize the eighth consciousness at all.