Ajata tells us that reality must be empty.
What is truly real is real eternally; an ultimate reality does not come and go.
Any so-called reality which represents any thing, material or non-material, will have had a beginning in time and thus will end in impermanence.
Nothingness is empty of beginnings or endings. Being empty of time, it is truly ‘eternal’: it knows of no change.
The lesson of advaita is that no element of you, a person, is real outside the context of the perishable universe.
And ajata tells us that anything which you, not being real, supposes is real cannot be real.
If there is any aspect of you which is ‘real,’ it is that you are nothing.
If there is any aspect of anything, which you consider to be real it is that it likewise is the same — nothingness.