Lua Finding time left in script countdown

[Grehy]

When using this object, I add a 60 second cool-down to it with this;

setGlobalStorageValue(45000, os.time() + 60)

To check if the cool-down is over, I use this;

if getGlobalStorageValue(45000) >= os.time() then
		doPlayerPopupFYI(cid, "The crane can only be used every 60 seconds.")
		return false
	end

But what can I do to find out how many seconds are remaining? Thank you

 

[Fallen]

doPlayerSendTextMessage(cid, 27, "Time Left: " .. getGlobalStorageValue(45000) - os.time() .. ".")