Hi Tom – great question!
It’s actually designed in such a way as to make best use of available space, so the number of columns varies dynamically according to the amount of horizontal space available.
If you’re at home dabbling in some code you can probably tweak things further in order to narrow or widen the default columns and so increase/decrease the number that appear within whatever space you happen to have available, though, so that could be worth keeping in mind 🙂
I hope that answers your question, but please let me know if I can assist with anything else 🙂