Sentence:  If you have an <WSD>unused</WSD> credit for a year for which you also have additional tax liability because of an early disposal of an asset, you may reduce the added tax liability by the current year's <WSD>unused</WSD> credit that may be carried back "solely" because of recomputation of the investment credit for the prior year. 
Meaning of the word marked with <WSD> tags:  Not used.