The "Skill based" option is there to see how efficient you are with different items for your avatars profession levels. Since a lot of items reach their maximum efficiency at a different profession level, there can be huge differences in your efficiency, compared to the regular chart. Some items may be highlighted. This means that the maxed profession data is missing, and the calculated values may be incorrect.

To make the skill based chart working you need to have done the following things:

1. Register an account. This can be done on the Account page.
2. Create an avatar. You must add your avatar in the Avatars chart.
3. Link your avatar to your account. This can be done on the Account page.
4. Add your profession levels. You can now add your avatars profession levels in the Avatar Professions chart. Make sure you choose your own avatar when making a new entry.

Your profession levels can be found in-game under RMB > My Avatar > Professions. It is also possible to capture your profession level using a capture tool and upload them to Entropedia. See Upload Avatar Statistics for more details. For the Weapons chart, you need to add both hit and damage professions, for the Medical Tools chart you need to add your Paramedic profession and for the Finder chart your Surveyor and Prospector professions. See the discussion tab for more info.

It is also possible to enter custom values for professions, without the need to register an account. These values will override the values from the Avatar Professions chart. It will apply to all the items in the list. When you don't fill in the boxes, the values you filled in the Avatar Professions chart will be used (in case those are not filled in, the value will be 0).

For more information how the skill based values are calculated, see here for weapons, here for medical tools and here for finders.