How do I get rid of NaN?

Hello! I have a simple code to get remaining time, getting first the unixtime/1000/60 to get the actual minutes. and adding this to a storage element, and then applying to a variable. That way I can - the variable to obtain the difference. but is giving me NaN. Anyone knows why?

Some help please :D

Its hard to say from the given information. I will say setting Local Storage every 0.1 seconds is a bad practice as its set up to be asynchronous, and will likely take longer than 0.10 seconds to complete occasionally.

Global, and local variables are a better match for this.

On item get - get item, isn't that a weird loop? I dunno if that has a strange outcome