DA14531 advertising data using user_svc1_adc_val_1_cfg_ind_handler

I am trying to send/transmit #define DEF_SVC1_ADC_VAL_1_CHAR_LEN  21 byte of data in the below service. But only 20byte data is displayed in that service. Is it possible to advertise data which is more than 20byte???

In user_custs1_impl.c

void user_svc1_adc_val_1_cfg_ind_handler(ke_msg_id_t const msgid,
struct custs1_val_write_ind const *param,
ke_task_id_t const dest_id,
ke_task_id_t const src_id)
{
struct custs1_val_ntf_ind_req *req = KE_MSG_ALLOC_DYN(CUSTS1_VAL_NTF_REQ,
prf_get_task_from_id(TASK_ID_CUSTS1),
TASK_APP,
custs1_val_ntf_ind_req,
DEF_SVC1_ADC_VAL_1_CHAR_LEN);

// ADC value to be sampled
memset(c_buffer, 48, sizeof(c_buffer));                                                      // I am firsr initailising the buffer data to zero
memcpy(c_buffer, buffer, sizeof(buffer));                                                    // I am copying the uart buffer[16] data in c_buffer[21]. I assume the data in c_buffer[16-21] is zero
memcpy(&c_buffer[16], buffer2, sizeof(buffer2));                                      // I am now copying LED write data in c_buffer[16-21]
req->conidx = app_env->conidx;
req->notification = true;
req->handle = SVC1_IDX_ADC_VAL_1_VAL;                                       // This length i have kept as 21byte where 16byte data i will send using uart and 5byte data i will write in LED   
req->length = DEF_SVC1_ADC_VAL_1_CHAR_LEN;                                     characteristics and append it in data[16] to data[20]
memcpy(req->value, calibrated_buffer, DEF_SVC1_ADC_VAL_1_CHAR_LEN);

ke_msg_send(req);

if (ke_state_get(TASK_APP) == APP_CONNECTED)
{
// Set it once again until Stop command is received in Control Characteristic
timer_used = app_easy_timer(APP_PERIPHERAL_CTRL_TIMER_DELAY, app_adcval1_timer_cb_handler);
}
}

req->conidx = app_env->conidx;
req->notification = true;
req->handle = SVC1_IDX_ADC_VAL_1_VAL;
req->length = DEF_SVC1_ADC_VAL_1_CHAR_LEN;                                               memcpy(req->value, &buffer, DEF_SVC1_UART_TRANS_LEN);             

ke_msg_send(req);

if (ke_state_get(TASK_APP) == APP_CONNECTED)
{
// Set it once again until Stop command is received in Control Characteristic
timer_used = app_easy_timer(APP_PERIPHERAL_CTRL_TIMER_DELAY, app_adcval1_timer_cb_handler);
}
}