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AD7788 increase the input range

Good day!
Read of theme "AD7788: Input ranges"
I have a question to the expert answer.  In documentation for REF3040 I found a similar circuit.

A specialist in the above subject, a similar connection recommended AIN- input to expand the input voltage. However, in the specifications for REF3040 input voltage range has not changed. Where the error lies?

Thank you!