It's an extra 5' for the climbing, and it may require a Strength (Athletics) check to climb successfully because it might be a non-trivial climbing situation, at the DM's discretion.
The rules don't provide clear guidance about the DC, or more importantly, what would happen if you fail this check. Under the circumstances, I'd say DC 10-15, depending on how smooth and slippery the edge is. And if you fail, you use up the rest of your movement for the turn, but you can still take your action. And if you use your action to Dash you can try the check again.