it is better ask them directly. anyway, it seems to be that the protein needed for the broilers, in this mix, was treated with phytase.
you can see:
Nutrition Research Reviews , Volume 13 , Issue 2 , December 2000 , pp. 255 - 278
DOI: https://doi.org/10.1079/095442200108729098
and
Kies, Arie K., 2005. Phytase studies in pigs and poultry. Effect on protein digestion and energy utilization. Doctoral thesis, Wageningen Institute of Animal Sciences, Wageningen University, The Netherlands.