Quote From monkia:
What is written in the one paragraph, do you think this paragraph is sketchy or strong? if you think it doesn't show your strength, you can ask the same professor politely to amend the letter. I know how it is daunting to ask professor multiples, but you have no other options, good luck.
I actually think it is quite strong besides its length. My worries arose after I googled about the length. I already thanked him, so I am a bit reluctant to ask for an amend.