It was increased from 1 billion to 3 billion in November 2017, then from 3 billion to 10 billion in December, then it was increased twice in February, to 15 Billion and to 25 Billion.
So this talk of "its been 15 billion for awhile" is nonsense. The company is preparing to dilute the heck out of its stock while pretending to do a buy-back.