成唯識論述記 6.98

6.98

述曰：此專注言，非是定心唯緣一物，即隨所注心多少境，或一剎那別欲注心處，深取所緣，定即得生，非要前後唯緣一境。

The Commentary states: This expression 'focuses exclusively' does not mean that the concentrated mind cognizes only a single thing. Rather, according to the intentional objects onto which the mind is directed, be they few or many, or at a single moment toward a particular place where one wishes to direct the mind, when it deeply grasps the intentional object, concentration can then arise; it is not necessary that across earlier and later moments it cognizes only one object.