Reference: Figure 6 of, ADXRS646-EP part datasheet.
We understand, Null Bias is ratio metric to Vratio input.
For Vratio of 6V, Null will be 3V(Typical). But in the graph (Vratio is mentioned as 5V) and Null bias is still 3V.
As per our understanding it should have been 2.5V
Vratio=5V is a TYPO in datasheet.