ADXL367设置FIFO采样长度后，使用轮询方式1s读取一次(非中断)，但和预期的不一致

I use the FIFO of ADXL367 and set it to stream mode, hoping to save 64 sets of X, Y, and Z-axis data with a sampling frequency of 400Hz. I poll the FIFO data every 1 second (without using interrupts), but I always find 513 data entries when reading the FIFO, which is inconsistent with the manual description. How should I configure it to achieve my desired functionality?

我使用ADXL367的FIFO，并设置为流模式；采样频率为400Hz，FIFO长度设置为64；我每隔1s轮询读取FIFO中的数据(不使用中断) ，但是我发现FIFO中总是513、512条数据，不是我预期的64个数据；有什么方式可以实现我的功能吗？

this is my code 

uint16_t adx1367_get_fifo_xyz(uint16_t *buff)
{
uint8_t data_buff[512 * 2] = {0};
uint16_t fifo_entries = 0;
uint8_t reg_val[2] = {0};

adxl367_get_register_value(&reg_val[0], ADXL367_REG_STATUS, 1);
if(reg_val[0] & 1 << 2){
adxl367_get_register_value(reg_val, ADXL367_REG_FIFO_ENTRIES_L, 2);
fifo_entries = ((reg_val[1] & 0x03) << 8) | reg_val[0];
if((0 == fifo_entries)){
return 0;
}

adxl367_get_register_value(data_buff, ADXL367_REG_I2C_FIFO_DATA, fifo_entries);
fifo_entries = (fifo_entries > SAMPLE_DEFAULT_AXI_HZ*6 ? SAMPLE_DEFAULT_AXI_HZ*6:fifo_entries);
for(int index = 0; index < fifo_entries; index++){
buff[index] = (data_buff[index * 2] << 6) + (data_buff[index*2 + 1] >> 2);
}
return fifo_entries;
}

return 0;
}

void adxl367_fifo_setup(void)
{
sample_mode_info_t *p_sample = NULL;
uint8_t reg_value = 0;

p_sample = sample_config_get();

// Set fifo stream mode
adxl367_get_register_value(&reg_value, ADXL367_REG_FIFO_CONTROL, 1);
reg_value &= ~(3);
reg_value |= ADXL367_STREAM_MODE;

// Set fifo sample x,y,z
reg_value &= ~(0x0F << 3);

// set fifo sample 64/1
reg_value &= ~(1 << 2);
adxl367_set_register_value(reg_value, ADXL367_REG_FIFO_CONTROL);

// set fifo sample 64/1
reg_value = 0;
adxl367_get_register_value(&reg_value, ADXL367_REG_FIFO_SAMPLES, 1);
reg_value = p_sample->sample_axi_hz;
adxl367_set_register_value(reg_value, ADXL367_REG_FIFO_SAMPLES);
}