1.
To knock off an amount from a price, time, or level means to reduce it by that amount.
Udinese have knocked 10% off admission prices...
When pressed they knock off 10 per cent.
PHRASAL VERB : V amount P n , V P amount
2.
If you knock something off a list or document, you remove it.
Tighter rules for benefit entitlement have knocked many people off the unemployment register.
PHRASAL VERB : V n P n , also V n P
3.
When you knock off , you finish work at the end of the day or before a break. ( INFORMAL )
If I get this report finished I’ll knock off early...
PHRASAL VERB : V P