Consideration of valuation changes in short-term investments in the calc of equity

Hi all, Schweser state that “only longer-term adjustments are made to stockholders equity. Thus changes in short-term investments are excluded.”

Given short-term investments are a component of Total Assets, and Equity = Total Assets - Total Liabilities, how can changes in short-term investments not impact on the equity valuation?

Thanks,

Frank

Anyone?!