This means (Skill points spent) / (Maximum skill points).
Every time you read a skill book, the skill points spent increase, until it is equal to the maximum skill points. Maximum skill points are initially equal to your level, but you can increase the value by completing some quests which give skill points as rewards.
Each class has its unique skills given from the start.
Unique skills do not have any steps or levels, so it cannot be learned.
Some skills come bundled together. When you learn one of them, you automatically learn the other called 'Alternative skill', and it costs one skill point.
This shows the current level of the skill.
You need to spend one skill point to learn a book. The requirements to read the next book in the series will rise. You must learn six books of the same skill to advance to the next level.
When a skill advances to the next level, the next skill starts from step 0 again.
You must read an appropriate skill book to increase an step of the skill.
Place a mouse cursor on a skill icon to see its description.
Shows all 4 levels of the skill series and highlights the current level with yellow color.
Shows the skill description including required MP and the other things.
Briefly explains how to activate the skill.