Hi @Thommy7571,
Efficiency values should not be interpreted on their own. See Design Diagnostics
You can try to create several designs, with different optimality criterion, run size, etc... and use the platform Compare Designs to compare and select the design best suited for your use case.
Design efficiencies are only a "summary" metric to help compare the performances of several designs, but I would recommend spending time on the different parts of the Compare Designs platform : Power Analysis, , Prediction Variance Profile , Fraction of Design Space Plot, Relative Estimation Efficiency, Alias Matrix Summary, Absolute Correlations ...
Hope this answer will help you,
Victor GUILLER
"It is not unusual for a well-designed experiment to analyze itself" (Box, Hunter and Hunter)