This guide will explain grading buttons on the Skritter website.
When you answer a prompt on Skritter, you can tap the screen to advance to the next prompt, keeping the automatic grading. You can also manually adjust the grade by using the grading buttons at the bottom of the prompt once answered. Once clicking a grading option, you will advance to the next prompt.
Tap the "forgot" button to mark the character as incorrect. This will reset the spaced repetitions as if the word is brand new.
Tap the "so-so" button to mark the character as correct, but see it sooner again than if you marked it with "got-it".
Tap the "got it" button to mark the character as correct. This is the standard correct button.
Tap the "too easy" button to mark the character as correct, and space it much farther than if you had marked it with "got it".
For a comprehensive guide on keyboard shortcuts, please refer to this guide.