When grading an Assignment module in GauchoSpace the grade inputted cannot exceed the maximum grade point (i.e. if the assignment is out of 100 points you can give up to 100 points, not 101 or more). To give points over the maximum (extra credit) there are two options, one is to use an override in the gradebook for the assignment and then input the desired point value, the other option is to create a separate extra credit grade item in the gradebook. The steps below explain how to accomplish both of these options.
To input an override with higher than the maximum point value of the assignment you can go to the gradebook, click on Single view.

Then use the Select grade item drop-down menu to select the assignment that you would like to input the override for.

You can then checkbox in the override column for the student you would like to put the extra points in for and you will then be able to put the point value in for them in the grade column (screenshot below with Ann Gaucho example).

If you would like to create a separate extra credit item you can do so in the gradebook by going to the Gradebook Setup.

At the bottom of the page click on Add grade item.

Input the name and maximum grade you want for the item and then expand the parent category section to then open the Grade category menu and then to place the item in the correct category then click on Save Changes.

Once the item has been created you will need to edit it to make it worth Extra Credit (cannot be done when initially created), to do so click on Edit next to the assignment in the gradebook setup and then Edit settings.

You can then check the box within the item to make it worth extra credit, then click on Save changes.

You will then be able to input points for this extra credit item in the single view within the gradebook.
Note: Make sure to adjust the "Weights" accordingly. For instance, making the weights 2% would mean that the highest / maximum grade students can get is 102%.