but I know that isn't correct because then I only get how old the product is for today and I need to see a whole range of ages.
In your 'sample data' you said you had one product and one sale date. Do you have several apple sales all with different dates and you want to calculate how long it's been since each sale? Or do you have one apple sale as per your sample and there's somehow multiple dates within that?
I'd suggest a good starting point would be to create a sample tableau packaged workbook.