Yup, it is just standard scientific notation numeric data, an absolutely ubiquitous format.
In Linux or macOS, you only need to run e.g.
awk -F ',' '{ if (FNR==1 || NF!=2) print ; else printf "%.4f,%.4f\n", $1, $2 } ' < original.csv > fixed.csvto convert the notation to decimal.
If you have Bash installed in any OS, run
bash -c 'LANG=C LC_ALL=C IFS="," ; ( read H && echo "$H" ; while read A B ; do printf "%.4f,%.4f\n" "$A" "$B" ; done ) < original.csv > fixed.csv'to convert the notation just like above.
In Linux, either of the above can be written as a script, with a shortcut that lets you drop files on top of to get them converted. (You can either discard the original data, save the original data to say
original.old, or use e.g. Zenity to pop up a Save As.. dialog for each converted file.)
If you have or install Python, it is easy to write a small program that fixes such CSV files. (Python 3 has a built-in
CSV module, that can read and write CSV files; or one can do the equivalent of the above awk line. Or you can even add a tiny Tcl/Tk user interface, so that when you drop a CSV file on top of the shortcut, the Python interpreter will execute the script, that will simply prompt you where to save the converted file.)
I personally don't use Windows, so can't be of much help there. Python is supposedly portable across systems... but to fix a problem, one has to first pinpoint or replicate the exact issue, and that is very difficult if you don't use the same operating system.