Interestingly this, combined with scars is really the only way we know how big giant squid can get. The largest that has been actually observed or caught is really quite small in comparison to the sizes indicated from sperm whale data.
I should add that this topic made me take a second look at giant squid data (what can i say, i think they are really interesting creatures). It does appear that large giant squid have been found dead but never seen alive or caught. Those seen in a well documented manor or caught have been around 25ft in length max, while the expected maximum size is around 60ft with the largest dead specimen being about 59ft long, although that was in 1878 so i don't consider it overly reliable data.