Null handling error when writing to sequential file

[sgubba]

My job calculates max and min values based on a column ....so i used a transformer with the column and added another dummy column with value 1. I use a aggregator use the dummy value column as key and then use the max value output function and min value output function.
I also use allow null output =False. Then i am writing the min and max value to a sequential file stage....

My sequential file stage throws a warning
Converting a nullable source to a non-nullable result

In the meta data for max and min columns i use nullable as No

......Why am i getting warning messages ...

Regards