>>>But... now it makes even less sense. Double time would mean half speed, wouldn't it? Instead of getting there in 10 seconds, it would now take 20.
>>
>>Doesn't "double time" mean "twice as fast" as the current speed?
>
>Actually it means "your sentence is doubled", as in "you'll be doing time... twice".

I guess it could mean a lot of things.
Context is everything.