LibreOffice Calc: Converting Numbers From Text To Numeric

I have Libre Office worksheets that contain columns of decimal data; however, that data is formatted as text data, not numeric data, and unable to be "calculated". Further, the data is left-justified in the column.

I reformatted the data in those columns as numeric data; however, while much of that data IS now recognizable as numeric data (and appears right-justified in the cells), there are now fields which contain alpha-numeric data!

What happened, and how do I fix it?

Thanks for the assist, guys.