Indicates the connection MTU, default 23 Measured in Bytes
See also
://cs.android.com/android/platform/superproject/+/master:packages/modules/Bluetooth/system/stack/include/gatt_api.h;l=543;drc=6cf6099dcab87865e33439215e7ea0087e60c9f2#:~:text=%23define%20GATT_DEF_BLE_MTU_SIZE%2023