SoftBank's Son turns $5.5 bn to $17 bn via buyback: Here's what's at play

The buyback will be funded by the proceeds from the 2.4-trn-yen initial public offering of the company's telecom unit in Dec

Call it the Masayoshi Son mathematical distortion field. 

The founder of SoftBank Group Corp added about 1.94 trillion yen ($17.6 billion) to the market value of his company Thursday — by unveiling a plan to buy back shares worth less than a third of that amount. Based on his own stake, Son's net worth rose by about $5 billion. 

The billionaire is no stranger to funny math. Yesterday, he opened his earnings presentation with a riddle: "25 - 4 = 9?" The formula is the 25 trillion yen value of SoftBank's assets minus 4 trillion yen in debt, far from being equal