Why does Davinci Resolve skip three frames at the beginning?

Why does Davinci Resolve skip three frames at the beginning of a clip?

I cannot move the red "marker" within the first three frames of a clip. I can put at every frame thereafter. What if I want to see frame 1 or 2? How do I do that?

Normally it doesn't, so I have to question what makes you think it is?

He's probably referring to "snap to" feature.

Yes, toggle Snapping on/off using the keyboard shortcut 'N', or click the magnet icon. You can also use the left/right arrow keys to move the playhead one frame at a time regardless of snapping.

Wow! That was exactly what I meant! Awesome, thank you very much.