connection interval & gap event length

[hrms]

I am trying to connect two peripherals to one central.
I do not understand the settings for connection interval and gap event length.

#define MIN_CONN_INTERVAL               MSEC_TO_UNITS(20, UNIT_1_25_MS)

For example, this would result in a connection interval of 20ms.

#define NRF_SDH_BLE_GAP_EVENT_LENGTH 6

For example, at this time, what is the unit of the gap event length? Assuming a connection interval of 20 ms, will the radio use time be 6 ms?