Who can explain why the current book value of the capital structure is likely to be different than a company's target capital structure?

Here is a part of the answer. Can you guys explin me why some maturities are going to benefit from the others?

Market Conditions:

D/E's market value will be different in the book and the capital structure due to the diverse market conditions. Some maturities, under those circumstances, are going to benefit over the others.