In Veda God is said to be both Sat and Asat
Ubhayatra Sadasat Samanvayah.
(In Veda and Gita the words Sat and Asat are used in contradicting sense, but they can be correlated to mean the same by logical discussion.)
In Veda God is said to be both Sat and Asat (Sadeva Somya.., Asadvaa…). But in Gita God represented by Para Brahman is said to be neither Sat nor Asat (Nasat Naasaduchyate). This appears to be a contradiction between Veda and Gita. Sat means existence. Asat means non-existence. Let us take Veda. When God is Sat, it means God is not Asat. Similarly, when God is Asat, it means God is not sat. Hence, the resulting concept in each statement of Veda combined gives the concept of Gita. Thus, Veda and Gita are correlated because Gita is said to be the essence of all Vedas.
God can be said as an item not having the existence of worldly items
Jneyapurvaastitvaabhaavashcha Vidyate cha Shruteh.
(The existence of Para Brahman is not the existence of non-God items in which the knowledge of the non-God items is a prerequisite condition. Para Brahman exists as per the statement of Veda).
All the non-God items are worldly objects, which are parts of creation. All these items are known first and then only their existence is mentioned. When you say that a pot exists, it means that you are stating the existence since you know the pot already. Hence, the existence of any worldly item requires the knowledge of that item already. If you do not know anything about an item, you will not say that it exists. Hence, the existence always requires the prior knowledge of the item. But God is beyond world and is unimaginable since God is not known. Hence, the existence of God is not similar to the existence of the worldly items. Since the existence of worldly items, which requires prior knowledge of the item, is absent in the case of God, God can be said as an item not having the existence of worldly items and hence God is non-existent (Asat) in this sense. This does not mean that God is really non-existent because God really exists as per Veda (Astityeva….) and hence God exists (Sat).