Holt_winters function and how to see the future

Hello
trying to use the holt_winters function

field(value) last() holt_winters(10,2)
group by time($_interval)

all done in the editor mode

the querie option is default exept Relative Time is 7d

but i can’t see the “future”
what did i miss

have a nice day
vinc

any help or idea? please