April 6, 1957

BN308-2 is a matrix number: Blue Note gave every tune it recorded the next number in one running series (BN308 is "Humph"), and the figure after the dash is which take of that tune was kept. Early on the series starts each tune's takes at 0, so -0 is usually the first try.

tk. 5 is the take as counted through the whole day, from the first tune to the last: the way the studio's log and, from the mid-1950s, Rudy Van Gelder's tapes number them. Later dates have only these.

On the earliest records (1939–40) the numbers in the matrix place, like 486A-1 or GM535-6, are the masters' numbers from the studios and pressing plants Blue Note used before it had its own series.