AuthData length 39

[krzysztof90]

I am using Fido2Net library.
Why AuthData is returning 39 bytes instead of 37?
I can't proceed with my verification because of that. When I skip 2 first bytes it verifies rp correctly but signature verification fails.
It calls fido_assert_authdata_ptr and fido_assert_authdata_len methods

[LDVG]

fido_assert_authdata_ptr() returns the CBOR-encoded authenticator data, i.e. a CBOR byte string. For 37 bytes of payload, this will be an extra tag plus length byte. If you instead need the "raw" authenticator data, use fido_assert_authdata_raw_{ptr,len}.