The data is being read as character strings, it can be do to many causes, like a non standard NA placeholder for example. We would need some raw sample data and the code you are using to import the data to give you any specific advice.
Another option for you would be to try parsing the numeric data afterwards with as.numeric()
If you need more specific help, please provide a proper REPRoducible EXample (reprex) illustrating your issue.