BLE Throughput Test not achieving data sheet mentioned data throughput

[SaadSid]

I am using Microchip RN4677 modules to test throughput. Datasheet say 64Kbit when connected to ios7. I am using RN4677 modules for both Master and Slave. Minimum connection interval allowed by module is 10ms. By theory max throughput should be (4packetsperinterval*20Bytesperpacket)/10ms nearly 64Kbits/sec but i am measuring it max to 32-34Kbits/sec. I checked it using C2540 packet sniffer and it shows that all the connection event is utilized and max payload is sent. Any suggestion how to debug this issue

 

[SaadSid]

After capturing some packets using packet sniffer i came to know that between time between end of connection event in one channel and start of connection event in next channel is around 17ms. I dont know if all BLE module have this much of gap