I am facing an issue with the SUM function of the redshift.

I just used 

```
SUM(col1) as T1 from "table_name" where ...

```

to fetch the data. Which have numeric type values in data type varchar of the column.

But it is not giving me correct total amount in T1.

An eg. col1 have two different row with the amount of "34.50". So it should return 69. But it is returning 68.

column "col1" data type is varchar.