When fields are created automatically as a result of a data import, the system tries to guess an appropriate length based on the first few rows of sample data. Sometimes this results in a field too short to contain the data.
To avoid this guessing process, create the fields before importing data.
To review or create fields, click Data, then All Records, then Fields.
If you have a field that's getting cut off, edit the field and view the actual field length as shown here:
If you save the field, the system will update the length with the option chosen in the Field Length drop down.