Get outpoint for a transaction
The output returned by bitcoin-cli listunspent is correct. As mentioned in document, outpoint is pair of (txid, vout)

txid is 4bbf676731987cce1e4639ec28d1219f065ab2aa5e9deb323c0b56bd0482d499. Its is hexadecimal representation of a binary string and will take 32 bytes, each hex digit is representing 4 bits (or half a byte)

vout is 0 , this is stored as uint32 in the bitcoin block and will take 4 bytes. In other words it stored as an unsigned int binary representation of 32 bits.