That's according to the PLO and quoted by Haaretz. Jews 'occupy' 1.1% of Yesha.
From news article:

Erekat stated furthermore that despite Israel’s continual policy of “occupation and settlement building,” an aerial photograph provided by European sources shows that settlements have been built on approximately 1.1% of the West Bank, thus legitimizing the Palestinian demand for a withdrawal to borders based on the June 4, 1967 borders.

According the CIA World Factbook the entirety of Yesha is 5,640 sqkm or 2,168 sqmi. 1.1% is 62.04 sqkm or 23.85 sqmi. That's the size of downtown Newark NJ or Oxnard CA. OR about 1/3rd the size of Washington DC, half the size of Tel-Aviv, one quarter the size of Damascus, 1/16th the size of Cairo, 1/23rd the size of Amman, or 3/4ths the size of the Beirut Urban Area.