No, you can not ad hoc points in Scorecard. Since it is query-based, there is no quick way to adjust or ad hoc points like you can in the Contest Engine.
However, you can manually adjust a metric by editing an existing entry. For example, I have a quarterly metric based on Calls, where I get a point for every task that I create that contains Call in the subject line. I currently have 4 calls in my Scorecard for this quarter.
If I want to adjust my score, I can edit my most recent task, Call and rename it Cal.l. After doing that and refreshing my page, my Calls metric is now at 3.
If I want to add points to my metric, I simply need to follow the procedure for this metric and start making dials and logging them into Salesforce!
NOTE: Your window of opportunity is based on the timeframe of the metric. For my example, it is a quarterly metric. So I have an entire quarter to manipulate it. However, after this quarter is completed, the number is locked in and I can't ad hoc it for that quarter anymore, just the current timeframe. So if you have a daily metric, you can only ad hoc it for that day.