Concatenating text with numbers

Hello, I'd like to ultimately produce a table using the report generator that has text headings in both the firs row and column; when I try to concat my data to the txt I lose the formatting on the data.

Currently my data array is a double and my txt strings are cells; I've tried a variety of combinations e.g. converting to strings, converting everything to cells and I still lose my rounding (the table displays relative error and all I would like to display is the whole number percentage).

Thank you in advance for your help; if it is also possible to format directly from the report generator that's a great solution but I'm relatively new to this tool.