יחזקאל מג:יז פירוש: רש״י

And the ledge, fourteen [cubits in] length The top of the altar, including the area for the horns and including the area for the feet of the priests, was 28 by 28 [cubits], and the 14 mentioned here were measured from its center, as is explained by “to its four sides.”

and the boundary around it Jonathan renders: and the rim, but our Sages explained it as referring to the horns.

half a cubit He measures from its center; hence it was a cubit by a cubit.