Erroneous Data when increasing sheet size

[CordingBags]

I have what I think of as quite a large worksheet, in a 5 sheet workbook.
This sheet is a Data Entry page for calculations on the other four sheets within the workbook.
I now need to almost double the width of this sheet, from columns K to DV to cover the columns K to IV
Row 4 contains the date for the entries within that column.

Surprisingly as soon as I add a new date the sheet almost seems to count the new entry and instead of appearing as a standard date, it is appended by a number, this number increasing as I add further dates.
Doesn't seem to matter how I format the dates I still get this additional "count number" appended.

If it is relevant the sheet is formatted as a table to enable filtering.

Any suggestions?

 

[CordingBags]

I have what I think of as quite a large worksheet, in a 5 sheet workbook.
This sheet is a Data Entry page for calculations on the other four sheets within the workbook.
I now need to almost double the width of this sheet, from columns K to DV to cover the columns K to IV
Row 4 contains the date for the entries within that column.

Surprisingly as soon as I add a new date the sheet almost seems to count the new entry and instead of appearing as a standard date, it is appended by a number, this number increasing as I add further dates.
Doesn't seem to matter how I format the dates I still get this additional "count number" appended.

If it is relevant the sheet is formatted as a table to enable filtering.

Any suggestions?
View attachment 60256

Removing the dates across the range produces Column count.

 

[CordingBags]

As I suspected this is exactly because the sheet is formatted as a table, the header row MUST contain unique values. Hence the suffix.