Operating system name and version: Centos 7 x86_64
Version of smsd: Version 3.1.15
Smsd installed from: sources
Name and model of a modem / phone: MTS 423s (Huawei E3531s)
Interface: USB

Good day, could You help me with multi-modem config?
I have server with 4 equal modems (in config are 8 described, but really 4 are inserted). Practically I got aggregate time of 4 sms send is 14 sec. Send time of 1 separate sms is 4-6 sec. How to reach aggregate time 4-6 sec spent for sending 4 sms?

my smsd.conf:

my top status:

my 4 sms sending log: