Client Deployment by using Remote Push and SEPprep

Dear C/O Symatec Technet team, and Experts of SEPM's,

I am using SEPM 12.1..5 RU5, i have download Client Install Package for Windows_x64 Client, and modified with SEPprep, i am trying to deploy client installation with remote push by selecting existing package, in the client selction wizard i have selected more tahn 10 client's, getting an error as client deployement push error, if i select lessthan 10 clients to deploy its working fine, i dont have an option to specify the maximum concorrent deployement, can any one Hero (Expert) suggest me where can i find Maximum concorrent deployement selection in Symantec Endpoint Protection Manager 12.1.5 RU5

Your Answerwill  highly appreciate....!

Regards

Sayied Anwer