But the original sentence is ungrammatical either way. Under your interpretation there’s still a missing “and”: “each measuring 18m x 7.2m and holding 30 people”.
The missing "and" is a tiny grammatical error, whereas the missing "," Someone mentioned is a large grammatical error. Tiny grammatical errors are OK -- language grammars change over time because many people start making the same tiny grammatical error until it becomes part of the accepted grammar of the language.