four groups of 80 engineered alterations

Are "four groups of 80 engineered alterations " referred to "four groups, each with 80 engineered alterations"?


Context:

Eager to share their enabling technology, the team published their results as CAGE reached the semifinal round. Results suggested that the final four strains were healthy, even as the team assembled four groups of 80 engineered alterations into stretches of the chromosome surpassing 1 million DNA base pairs. "We encountered a great deal of skepticism early on that we could make so many changes and preserve the health of these cells," Carr said. "But that's what we've seen."

More:

http://www.sciencedaily.com/releases/2011/07/110714142130.htm