You are missing single quote signs ' in your formula, it should be VALUE(NAME(ITEM('02Hours'))) - 1
However, as @JaredDolich already indicated, try to follow best practice and create System Module to perform any calculations and store attributes instead of creating properties. As one of the reasons, it would be also easier for you to write the formula after typing VALUE(NAME(ITEM( you can then just click on the list name. This way, you will always get proper list name and add single quote signs automatically. It will make things easier for you!