undefined

Hi, Manjula 

If you can change the value successfully and without error then you can ignore this warning.

But If the data type is supported, but there are values that are not supported within the new data type, you will get another error, and will need to correct the data values before proceeding.

The meaning of the second half of the statement "...., you can restore the column by refreshing the table"

it should be related to power bi data structure. The change data type operation will be applied a 'change data type' step to the backend query table then power bi will force update the data model table fields to sync the records structures.

This operation has not affected the raw data structure which cache in previous query table steps.
If you change back the data type and do refresh operations, power bi will re-generate the data model tables based on the backend query table structure and these data type meditation will be restored. ('restore the column by refreshing the table' mean the use refresh feature to re-generate the data model table with raw table structure)

refer:

Changing Data Type of a Column

For more information about data types, you can refer to the following documents

Set the data type of a column in Power Pivot

Data types in Power BI Desktop

Hope this helps.

Best Regards,
Community Support Team _ Zeon Zheng

If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.