It isn't treated differently on your federal tax return; just enter the K-1 in the K-1 interview of the Business Investment and Estate/Trust Income section of Wages and Income.
When you come to the Ohio return, the interview will have a screen for adjustments to federal item; this screen typically starts with "Here's the income that Ohio handles differently". One of those categories will be "Depreciation adjustments".
By "add 5/6th back on your ohio income tax return, they mean to multiply the federal bonus depreciation in Box 17, Code V by 5/6 and enter the result as an adjustment. The effect of making this adjustment will be to increase your IL taxable income by the amount of the adjustment, by decreasing the depreciation claimed for IL.
