Expression explanation:
"Up to eleven", also phrased as "turn it up to eleven", is an idiom from popular culture, coined in the 1984 movie This Is Spinal Tap, where guitarist Nigel Tufnel proudly demonstrates an amplifier whose volume knobs are marked from zero to eleven, instead of the usual zero to ten. The primary implication of the reference is one in which things that are essentially the same are seen as different, due to mislabeling or the user's misunderstanding of the underlying operating principles. A secondary reference may be anything being exploited to its utmost limits, or apparently exceeding them.
Source and further reading: en.