Allowable settlement is a serviceability limit, if project documents didn't specify certain value you can use the allowable settlement  of shallow foundations ( I think most codes specify 100 mm as the allowable total settlement for shallow foundations).

Dear George,

pl find attachment.

http://www.iitgn.ac.in/gise2015/lecture-handouts/Lec4_Piled%20Raft.pdf

http://www.iitgn.ac.in/GISE2014/handouts/AP-Optimizing_Foundation_Design_and_Geotechnical_I.pdf

http://www.sefindia.org/forum/files/pile_group_settlement_estimation_harry_poulos_177.pdf

As Ahmed says, it is a serviceability limit. What will happen if it settles?  Is the settlement likely to be uniform?  What will happen to facades?

These questions must be answered first, to determine the allowable settlement

I think 25 mm settlement is better fo service condition. This concept parallel with concept of q-all, that is q at settlement 25 mm

The Maximum value is 100mm

As I said above, Mala, it all depends. 100 mm in 20 m between piers is too much. 100 mm in 400 m is barely noticeable.