John Lennon’s remarkable first solo album, the soul-baring John Lennon/Plastic Ono Band, was released in the US and UK on 11 December 1970.
All these songs just came out of me. I didn’t sit down to think, ‘I’m going to write about my mother’ or I didn’t sit down to think, ‘I’m going to write about this, that or the other.’ They all came out, like all the best work of anybody’s ever does.
Lennon Remembers, Jann S Wenner
In the United Kingdom it peaked at number eight on the albums chart. It fared slightly better in the United States, reaching number six.
One single was issued from the album. ‘Mother’, backed with Yoko Ono’s song ‘Why’, was released in the US on 28 December 1970. It was not a success, peaking at number 43 on the Billboard Hot 100.
John Lennon/Plastic Ono Band saw the closure of a chapter of Lennon’s past, a fresh beginning with a blank page, and a cautiously optimistic look towards the future. His subsequent career had its highs and lows, both commercially and artistically, but never again would he release a collection with such consistent vibrancy, purity and revelation.
All We Are Saying, David Sheff


The notes say that the album peaked at #11 in the UK, but the Official Charts entry online shows it peaking at #8: https://www.officialcharts.com/albums/john-lennon-john-lennon-and-the-plastic-ono-band/
It spent 11 weeks on the UK charts, that might have been where the reference to 11 came from.
Thank you Michael. I’m not sure where that number did come from but I’ve made a correction.