Exporting values based on data in a field

I have an employment intensity indicator form field that requires a value to be exported between 1 and 8 but also needs to have a 'real' value that is used in calculations.

For example, if someone input 35 (hours per week), the field would have an export value of 8 (gov code), but the 35 would still be able to be used in other calculations running on the PDF. 

These are the constraints I need to use to allocate the export value:

ILR Specification: Attribute field: Employment intensity indicator - GOV.UK (submit-learner-data.service.gov.uk)