Krishna says, "O Arjun, know Me to be the beginning, middle, and end of all creation. Amongst sciences I am the science of spirituality, I am logic in arguments" (10.32). Referring to the same spiritual knowledge, Krishna earlier said that when you realise this, nothing more here remains to be known (7.2).
The essence is to know the self. Krishna calls the knower of self Yogi and says he is superior to 𝙎𝙖𝙨𝙩𝙧𝙖 𝙅𝙣𝙖𝙣𝙞 who has read numerous texts but is still not aware of self (6.46). Krishna gave a path to attain it when he said, "Know 'that' by prostration, questioning and service, the wise who have realised the Truth will teach you the knowledge" (3.34).
Essentially, any knowledge which dissolves our 𝙖𝙝𝙖𝙣𝙠𝙖𝙖𝙧 (I am doer or I am knower) is spiritual knowledge. It could be history, physics or medicine where the more we learn the more is left to be learnt, they all have the ability to make us realise that we are just a 𝙣𝙞𝙢𝙞𝙩𝙩𝙖 𝙢𝙖𝙩𝙧𝙖 (an instrument) in the hands of the almighty. It is any knowledge that helps in the dissolution of 𝙖𝙝𝙖𝙣𝙠𝙖𝙖𝙧 like how the salt doll dissolves in the ocean.
After spiritual knowledge, Krishna mentions logic which is nothing but questioning. It is not the logic we use in an argument to prove a point, but it is that logic to find the ultimate truth or spiritual knowledge.
Krishna further says, "I am the beginning “A” amongst all letters; I am the dual word in grammatical compounds. I am the everlasting Time, and amongst the creators I am Brahma" (10.33).
Earlier Krishna said that he is time among measurers and now he says HE is the eternal time. It is the time that creates everything and destroys it in due course. But time never changes and HE is the eternal time.