Format better suited to feed to a script:
$ sudo pfctl -vsl mail-in 1664158 1601986 763762591 887895 682427415 714091 81335176 mail-out 2814933 2711211 492510664 1407278 239776267 1303933 252734397
pfctl Verbosely Show Labels
label, evaluations, packets passed, bytes passed, packets in, bytes in, packets out, bytes out
For periodic data, use
pfctl -vszl
pfctl Verbosely, Zero-out afterwards, Show Labels