As the word contuzo is spelled contuso in contemporary Portuguese, I was able to find easily some examples of the usage, namely a English-Portuguese and Portuguese-English dictionary from 1827.
(1827) - http://books.google.com.br/books?id=mUw8AAAAIAAJ>
To Contuse, v.a. contundir, pisar, moer, fazer contusão.
Contused, adj. contuzo, pisado.
Contusion, s. contusaö, pisadura na carne.
(1827) - http://books.google.com.br/books?id=pTtBAAAAMAAJ>
Contundir, v. a. to squash, to crush, to beat, to bruise flat.
Contuzao, s. f. a contusion, or bruise, (in surgery.)
Contuzo. See Contundir
Also, I found a mention on a light contusion suffered by Marechal de Campo Brown in the Battle of Passo do Rosário (20 February 1827), of the Cisplatine War (War of Brazil, for the Argentinians; War of Independence, for Uruguay). This light contusion is said to have been caused by a musket ball.
The casualties report is of course to be seen as the receivers end, that is, the end results of the fight in the viewpoint of the regimental surgeon.
Jorge