It means your post is replied to and thereby moved back up on the list.
So that people will be more likely to see it when they check the recent post.
My manuals are 72 an 73. Yours is a older?
Yeah,I bought a manual on ebay because it was advertised as corect for the 64 barracuda and it only had about 4 pages for my car added on at the back! Very little reference to the 273. 60 bucks out the window....