How many seats were open over time, on the primary market and on the resale market, oldest first, one point per reading. The two markets are read in one pass and stamped a few seconds apart, so readings within 300 seconds of each other are ONE point, stamped with the later of them. Null on a market means that pass did not read it, never zero. Up to 30 days back, and it stays at that cap rather than erroring. Costs one unit whatever the days value.