The graph is guessing (or interpolating). If you select ‘show missing data’ in top left, you will see the actual data points it has. The in between ones are estimated.
The Feed update rate is 60s, the Input (incoming) data rate is 3 minutes. The 3 minute rate is not adjustable and I think that the only way to change the feet rate is to make a new feed (and lose current data). Is that right?
I could send the 3 minute data every 60s even though for those 3 minutes the data does not change.
I modified the Input Data Rate (externally) so that a datum point is sent every 60s. This has fixed my problem. I now understand a bit more about Feed Rates vs Data Input Rates.
Also, what type of feed is it? PHPFina or PHPTimeSeries, or something else? The Graph display varies as to what it does in the way of interpolation and missing data depending on the feed type as well as the sampling interval as already noted.