Translation:Of course they have useful tools for the garden.
I think it means both depending on context.
I am not a truly fluent speaker yet but I have a lot more experience and practice with Esperanto compared to when I posted the above question. Nevertheless, take what I am about to say with a grain of salt, since I am not sure it is true or not, I am just basing it around what feels right to me, now that I have used the language quite a few times.
In English the difference between "understandably" and "of course" is that "of course" carries the sense that the statement should be obvious. In Esperanto, if you want to be absolutely clear, I guess you would have to build your sentence in a different way. If you want to remove the sense of obviousness you could say instead, for instance, "Oni povas kompreni ke...". On the other hand, if you want it to be unmistakably clear that you mean to say that the statement is obvious you can say something like "ne surprize" or "evidente".