A single transaction can include multiple payments, this process is called batching and is a more efficient way to send funds to multiple recipients, and the average number of payments per transaction has changed over time. For that reason, while the bitcoin network is composed of block of transactions, looking at the number of payments is a better indicator of the general network activity. Payments are accounted for only once their transactions are included in a block.
Due to the anonymity of bitcoin transactions with the use of addresses, the number of payments is not exact and should be estimated from the type of transaction. We have assumed that any transaction outputs is a payment, apart from one output being the change of the transaction when there is at least 2 outputs. For example, a transaction with 1 output is assumed to be 1 payment, and a transaction with 10 outputs is assumed to be 9 payments. This methodology can be improved, for example by detecting and removing payments from transactions consolidating UTXOs or entities moving funds from cold to hot storage.