Because I work in Excel all day, I run into junk like this all the time and thought I would take a stab at this.
If you are entering your IDs as 3-digit IDs that are only separated by commas in your Excel file, then I can almost guarantee that Excel is viewing what you intend to be a string as a gigantic number. One quick way to test it is to put an apostrophe in front of the string of IDs - forcing Excel to view this as text. That should more-than-likely solve your issue.
Your other problem could be that you have a ton of commas - and you are saving to “comma separated values.” Those commas could be seen in the CSV conversion as separators for the cell values. I believe in Excel when you export, you can specify what you want delimiting your values in the CSV file - you might try selecting TAB and see if the CSV file will interpret your data more accurately.
But, that doesn’t explain the 000,000,000,000 pattern in your CSV screenshot. I think that you are getting that result because Excel is seeing your string as a huge number.
Let me know, okay?
I can throw some more ideas at this if need be.