"People really aren't supposed to mess with time, according to the powers that be." Not that Bulma genuinely cares about that, really. It's just the fact that she doesn't want their world to be imploded that makes her even think about it twice so far as making another time machine to continue on as if Beerus hadn't already warned her.

"I was trying to build a second one and Beerus destroyed it before I could complete it." Bulma sighs, trying to think of a simple way to explain this whole thing. Their world was pretty strangely complicated, when it comes to things like time travel and the lot.

"Yes, Future me made one for Trunks to use and come back in time with. He used the same one the second time he came back, and I went to the Future with them, that time." But oh, wait -

"Trunks doesn't want to hear about anything past his time, though, so... you know. Keep that between us please."