It looks like an index column. It should not affect the analyses you are trying to do.
There are several uses for the index column. For instance, you can use the index for explicitly analyzing or subsetting your data.
You can check to see if that is an index column or not by looking at the shape of the data.
If this is pandas dataframe, you could try
df.shape
and it should show the actual dimensions of the data (without the index included). So for the example table you provided, the result would be - (21, 7).
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