अस्ति ब्रह्मेति चेद्वेढ़ सन्तमेनं ततो विदुः' इति श्रुतेः ब्रह्मास्तीति ये विदुस्ते सन्त:, तैः प्राप्यत इति सद्गतिः ; सती गतिर्बुद्धिः समुत्कृष्टा अस्येति वा सद्गतिः ।
In plain words
Scripture says: "If a person knows that Brahman is, then the wise count him too among those who are." So those who know that Brahman exists are the sat — the ones who truly are. He is what they reach, and so He is Sadgatiḥ, the goal of the good. Or read it the other way: gati means understanding, and His understanding is true and utterly exalted — so He is Sadgatiḥ on that count too.
Close to the Sanskrit
"If he knows 'Brahman exists', then they know him as existing" — thus from the śruti. Those who know 'Brahman exists' — they are the sat; by them He is attained: thus, Sadgatiḥ. Or: His gati, that is, His understanding, is true, supremely exalted — thus, Sadgatiḥ.