Letsencrypt: Failed to request certificate : Missing or non-numeric months before renewing

Letsencrypt certificates are issued for max 3 months. Virtualmin SSL configuration permits only 1,2 or 3 months as valid input for "Months between automatic renewal" The problem is: If I want to renew the cert at 3 months, in the last day of the cert validity, browsers will complain about an invalid cert date. Maybe I missed something, but if a cert is valid until 24.11.2016 and the current date is 24.11.2016, the browser will throw an invalid date error. Would be helpful to be able to setup the value with days also, like 2.28 (2 months and 28 days) to prevent such issues and also to prevent too many cert requests to LetsEncrypt. At the moment, setting the value to 2.xx or 2,xx throws the error: Failed to request certificate : Missing or non-numeric months before renewing