Beginner Question: How to tell 273LA from 318?

On my 1965 Dart, which is supposed to have a 273 cu in, the block has 2465330-4 stamped on it. I looked at the "How to ID a Small Block" post, but my stamping doesn't seem to add up. I don't see "273" in the stamping.

Can anyone decipher the 2465330-4 engine code?