A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
Try changing -10 to -11.
R1C15 means cell O1. When you inserted it will become P1 so you should use R1C16.
Similarly R1C12 was L which has become P so C12 should move to C13. You got this part right.
Now Match RC[-10] would have takend you to Col E on the sheet containing the formula. Is that what you want? If not then you will have to adjust -10 accordingly.
You are right though, it might be a good idea to record the macro again and then compare what has changed so that you understand it better.