ज्ञानं तेऽहं सविज्ञानमिदं वक्ष्याम्यशेषतः। यज्ज्ञात्वा नेह भूयोऽन्यज्ज्ञातव्यमवशिष्यते ॥

jñānaṁ te ’haṁ sa-vijñānam idaṁ vakṣhyāmyaśheṣhataḥ yaj jñātvā neha bhūyo ’nyaj jñātavyam-avaśhiṣhyate

I will declare to thee this knowledge and wisdom in its completeness, which, having known, there is nothing more here needeth to be known.

In plain words: Krishna promises to teach both knowledge and deep understanding completely. Once Arjuna knows this, nothing else will be left for him to learn.