Of course your are right in a literal sense. But if the crew were more than say 150, the author would have said "more than 150 men."
30 guns at 3.5 men per gun (an average from various references) would be 105 men, add in another 30 to run the ship and I can envision a crew of 135 to 145 as appropriate. This is a large crew.
I bet the reality was more like 100 men, and the guns were not fully manned. If the guns were loaded ahead of time and only primed just before firing, a crew of 4 could fire a gun and then secure it without reloading. They could then fire a second gun, possibly staying with it to reload. This would produce rapid initial fire with much slower sustained rates.
Also, keep in mind that 40 guns would just be 20 guns on each side, and most of the time you would only be shooting from one side.