the speed of large amount of data

Question

int main(void)
{
uint32_t BufferCount;
uint32_t err_code; 
 // Initialize
leds_init();
timers_init();
buttons_init();
uart_init();
ble_stack_init();
gap_params_init();
services_init();
advertising_init();
conn_params_init();
sec_params_init();

simple_uart_putstring(START_STRING);

advertising_start();

// Enter main loop
for (;;)
{
 //power_manage();

	err_code = ble_nus_send_string(&m_nus, "SSSSSSSSSSSSSSSSSSSS", 20);
	if (err_code != NRF_ERROR_INVALID_STATE)
	{
 APP_ERROR_CHECK(err_code);
	}

	nrf_delay_ms(20); 
	<font color=red>/*
	Here, if the parameter is set to 20 even after the mobile phone to be wrong, not the error is set to 50,
 
 But because of the large amount of data, should be set to 20 to send all data
If this is set to 20, modified to ensure even mobile phone without error in what place?
*/ 
 //for debug 
	BufferCount++;
	if ((BufferCount%100)==0)
	{
 ble_nus_send_string(&m_nus, "IISending Data", 14);
 nrf_delay_ms(50);
	}
}
 
 } 
 /** 
 
 @}
*/