"Easy" way to modify Craft time?

Greetings.

I try to modify crafttime for a small amount of people in a group...

but if i use this-

Code:

    task.blueprint.time -=  task.blueprint.time / 2

it just reduces the task everytime its done by half. so at the end its instant....

some rather easy way to prevent that?

 

better to write:
task.blueprint.time /= 2;

not means it works but you write more code than needed ^^