Same Speed With Delta?

I have the standard top down zombie bashing game. I use the standard {x += velocity * delta * dampener} system of moving. But the thing is, I need the speed to be exact. So how do I make it so that delta won’t make the speed different than what I want. Say delta is 2. Then instead of me heading .3 pixels an update, delta will make it .6. How do I keep it at .3 ppu?