Seeed xiao bluetooth comunication increasing sampling rate

Hi! Thanks for the response! @PJ_Glasso @liaifat85

I try to put 2

#define FAST
#ifdef FAST
#define CONN_PARAM 2 // connection interval *1.25mS, min 6
#define DATA_NUM 244 // max 244
#else
#define CONN_PARAM 16 // connection interval *1.25mS, default 16
#define DATA_NUM 20 // default 20
#endif

but then the output of the peripheral is like this:
PHY ----------> 2
Data length → 251
MTU ----------> 247
Interval -----> 16

so, now the interval is no more 6, neither 2 but it is 16. And the output of the central is still:

Sampling Rate: 19.00 packets/second
Bit Rate: 37088.00 bits/second
Sampling Rate: 19.00 packets/second
Bit Rate: 37088.00 bits/second

any suggestion? do I need to change anything else?