You are graded on your ability to communicate, in english, with a rittan formet. Ef u wrote lik3 this, u wood probably not FaiLZ; bUt if I wear teh gradar, I wood f4il u 4 being ubnacktious.
Seriously, you ARE graded on your written communication. you ARE graded on your english. But I highly doubt you would suffer any if you put CBC, BMP, CXR instead of "I will get a CBC, BMP, and a CXR" Know what i mean? Write the note the way you would expect it written in a dictation, so you cannot go wrong.
They won't count against you if you have a mistake sprinkled in here and there as they know most people are under time constraints. However, if your grammar and spelling detracts from your ability to communicate via writing then yes, I can see how that would affect your overall outcome.