"MaxConcurrentConfigRequests"
core setting controls number of simultaneous policy requests from clients.
You would like to increase the default value to something higher so more client machines can obtain their client configuration.
ITMS 8.7.x
MaxConcurrentConfigRequests
has a default value of 10.
Maximum hard cap is 100 for ITMS versions 8.7.2.
And 500 for ITMS version 8.7.3 and later.
See "Updating Core Settings in ITMS 8.5 and later" (KB Updating Core Settings in ITMS 8.5 and later) in order to make changes to Core Settings.