lop off

Reader's Digest 6月号の記事、The 20 tips health experts beg you not to skip　- ENERGISE YOUR LIFE の中のThe Motivation Expertによる助言、Get results in 20 secondsから引用します。
The difference between having a goal and actually accomplishing it? Just 20 seconds, says positive-psychology guru Shawn Achor. Researchers have learned that if we can lop 20 seconds off the start-up time required for a task, we're much more inclined to follow through.
文脈から考えると "lop 20 seconds off" は20秒を削ることだと思いますが、確認します。
・Collins English Dictionary: tr usually foll by off: 1.to sever (parts) from a tree, body, etc, esp with swift strokes 2.to cut out or eliminate from as excessive: The first section of the line opens next year - if all goes according to plan - and will lop up to 15 minutes off journey times.
・Infoplease Dictionary: to eliminate as unnecessary or excessive: We had to lop off whole pages of the report before presenting it to the committee.
・Cambridge English Dictionary: to reduce a price or the amount of time taken to do something by a particular amount: He lopped eight seconds off the record.
そんな訳で今日は確認後のコメントを "lop off" します。