I hope you have solved it in the meantime!
I have problems with importing numbers because the data I have in csv, extracted from the bank site and from paypal, consider the dot as a decimal separator and the comma as a separator for thousands, while airtable reasons the other way around.
The solution I found is to convert the numbers to text format in excel, replace commas with nothing and replace periods with commas and then use the copy/paste function directly on the table.
I hope this solution will be useful to you.