On the 10 minute tab, it says reports 637k items for the last 10 minutes, and either 64.0k/m or 63.9k/m, which doesn't match up. I'd expect it to either say 637k and 63.7k/minute, or 640k and 64.0k/minute
Printing out the actual statistics
with this command
/c game.player.print(game.players.force.item_production_statistics.input_counts["angels-ore1-crushed"] .. ' ' .. game.tick)
several times prints out
This works out to 650832 items created in 36609 ticks, slightly more than 10 minutes. This is 17.777768660084522 items/tick or, assuming 60 ticks/second, 1066.6661196050713 items/s, exactly what I expect given that I am creating 16 fully saturated 'Ultimate' belts with a speed of 66.67 items/s for a total of 1066.667 items/s.
If we assume the 637k in 10 minutes number is accurate, that would mean the factory had to create between 21-22 items/tick for the extra 609 ticks in the above interval (depending on if raw number displayed rounded/truncated in the chart was 637000 or 637999 items), which is simply not possible with how the factory
is setup. Presumably this would be also visible on the chart as that is nearly 20% higher than average the average.