The Expense Grid has 14 default expense categories, and for each category, there is a corresponding table. For example, Taxes, Insurance, Management, and so forth, qualify as categories.
These tables simply help to visualize that particular expense averaged across all of your comparables. You are not able to directly modify these tables.
To access these tables, simply select the Navigate function (CTRL+SHIFT+N) and transition to your desired table via the right-most section column.