The good news is that the bottom door seal can be replaced fairly easily. The seal is measured by the width of the seal. In the above picture you can see the seal partially installed in the bottom door retainer. If you were to remove the seal and lay it flat you could accurately measure the width of the seal. Most of the Raynor doors come standard with the 3" seal. If your garage floor is uneven or has some dips in it then the 4" seal can be used to help fill in some of those gaps.
Installation Tips: After you pull the old seal out of the retainer take some soapy water and put it on the aluminum retainer. Then pull the new seal through the retainer. The soapy water will make it much easier to pull. Once you have the seal installed take the extra inch or so of seal on either end and tuck it back into the retainer....this will help keep the seal in place.