If that is the case, it's hard to say...I don't think it would be as big a problem if your GP initialed or made some kind of note about the error. (When the murse misread my lab result and then crossed it out, I told her to please initial next to it.) It is also highly plausible that it won't matter at all, especially since they did not cite any special criteria about making corrections on the original form, i.e. use only blue ink, or no white out, or obvious corrections. I don't yet know how they handle denying medical clearance, but it seems more likely that they would send you a new form and ask you to fill it out again, before they would revoke your grant. If you made a copy and have all the pertinent information, then it should only be at the worst an inconvenience.
Sorting through minutae... it never ends...does it?
Hope this helps!