A compound field with a text field and paired integer field.
There is now also a submodule called textintegerfieldx2url -- that's two text fields, two integer fields, and a URL field. This is unlikely to fit your exact needs but it is another example you can copy for making compound fields.
- Freeform allows people who can add content on your site to define their own labels for certain fields, or to provide their own units. Same exact compound field idea, but slightly different use case.
- Field Collection is better if you have more general needs of associating fields. For performance and control over display of input forms and output, Text & Integer Field is better for the precise need of paired text and integer fields. See also Relation module, which has similar underlying concepts (relate entitities!) as Field Collection.