littleskunk explained why it is like that… apparently the satellites which perform the math, off all the nodes, which ofc takes a while, it completes a cycle in less than a day and then updates the numbers, which are plotted on the graph… but then because its always less than a day tho depending on workload, then it will eventually manage 2 or maybe even 3 updates in a day… while other days it might only do one or maybe even skip one… which is then added in the next day…
its because the data is accurate that the graph is inaccurate 
the avg is correct, the timing it takes to complete is dependent on work load ergo a time factor… and the graph displays numbers over time, and thus the inconsistent time factor makes the graph look inconsistent…
Keep Calm
And
Keep Storjing