Speaking, I would say 'a thousandth' or 'a tenth of the percent'. Applying 'a' in lieu of 'one particular' in declaring It appears nicer. More, in exposition, 'a' can be an indefinite article, which indicates the speaker won't know the identity of your noun, in this case the thousandth in https://rowanmkewn.blogscribble.com/36726637/bulk-thca-flower-secrets