In Monero transactions can be locked for a period of blocks or until a certain UNIX time. All the outputs of a transaction are locked together. All coinbase/miner transactions are locked for exactly 60 blocks (as of protocol v12). It seems clear that an output from a transaction with UNIX lock time can be spent in a block with timestamp greater than or equal to the UNIX lock time.
Question: is the unlock block height the first block that an output is spendable, or the last block it is unspendable? E.g. block 1 published, coinbase unlock_time is block 61 (current block + 60), can the coinbase be spent in block 61 or must it be at least block 62?