What is the meaning of the "sign of fatigue from staring" of the tathāgatagarbha mentioned in the Śūraṅgama Sūtra?

The sign of fatigue and contact of the tathāgatagarbha is caused by the manas; the tathāgatagarbha itself does not have fatigue, contact, or the sign of fatigue and contact, because it has no mental engagement with the dharmas of the three realms. The tathāgatagarbha, whose mind-nature is quiescent and extinguished, ceaselessly gives rise to various dharmas following the manas' continuous grasping, and has no choice but to use the eyes to see forms, the ears to hear sounds, the nose to smell scents, the tongue to know tastes, the body to feel tangibles, and the mind consciousness to discern dharmas. Thus the signs of fatigue and contact of the six sense bases (ṣaḍāyatana) appear.

If the manas does not grasp at the various dharmas, the tathāgatagarbha abides in quiescent extinction and will not give rise to any dharmas; the functions and activities of the six sense bases will not be produced. When deluded dharmas do not arise, the tathāgatagarbha abides in the true, unmoving, wondrously profound and serene. Originally the tathāgatagarbha gives rise to no dharma whatsoever and is unmoving with respect to all dharmas; but when karmic seeds ripen, through these conditions it stirs delusively, and the various dharmas must inevitably be born. As soon as the various dharmas are born, that is fatigue and contact—being forced by the manas. Yet the tathāgatagarbha has no thought or notion of being forced, nor does it know that it is being forced; it simply acts in accord with conditions, spontaneously, without any other thought.