Are these regular products or special one offs?
Take a look at my daily specials setup, might give some ideas;
Either way would be using settings values with, If its regular products setting name would be something like countdown_{product name} and you could set by say having an order mapped command to set countdown value and pull product name because order would be selected so can grab the name and enter number with a ?prompt.
Also could even set custom header on menu item to pull the setting value using I guess either $1 or {0} depending on which works.