Translation:April, June, September and November have thirty days.
Not an Esperanto expert here, but some personal experience may be of use...
I would think the latter. This construct looks Slavic to me, and, being a native Russian speaker, I've seen both. It's pretty much the difference between "X and Y have Z days" and "X and Y each have Z days." Only used with quantities, though.
I'm sure I could dive into the Esperanto grammar for a few hours and fish out chapter and verse, but this is the way it makes sense to me :)
Please feel free to slap me around a bit with a large trout if the above is incorrect.