ImportFromWeb will try to detect numerical values and convert them into the appropriate format. It usually works well when the format of the extracted values are compatible with the spreadsheet’s locale.
You can check your locales from the menu > File > Spreadsheet settings
If you prefer to keep your spreadsheet settings as is, you can try to transform the content returned by ImportFromWeb. For that purpose,
- you can use the Google Sheets function you are used to (SUBSTITUTE, REGEXREPLACE, etc)
- You can use regular expression right into the function. See more