If you look at the docs for the chart node it shows the data should be formatted like this
[{
"series": ["A", "B", "C"],
"data": [
[{ "x": 1504029632890, "y": 5 },
{ "x": 1504029636001, "y": 4 },
{ "x": 1504029638656, "y": 2 }
],
[{ "x": 1504029633514, "y": 6 },
{ "x": 1504029636622, "y": 7 },
{ "x": 1504029639539, "y": 6 }
],
[{ "x": 1504029634400, "y": 7 },
{ "x": 1504029637959, "y": 7 },
{ "x": 1504029640317, "y": 7 }
]
],
"labels": [""]
}]
In your data array you have the properties Time and Poly_Level instead of x and y.
If that doesn't work fix it then feed the output of the function into a debug node, and show us what it shows.
