I'm confused how the book obtained the value of 36% near $40,000. What is the math behind that number?

ACCOUNT INCREASING IN VALUE Assume that as an initial transaction a customer sells short 1,000 shares of ABC at $100. The account sets up as: Credit $100,000 +50,000 $150,000 Short Market Value = Equity % $100,000 $0 50,000 $100,000 $50,000 SO If the market value of the stock nises to $110 at the end of the day, the account now shows. Credit $150,000 Short Market Value = Equity% $110,000 $40,000 36 A picture of this shows