Does this exist and how would I find it if it does?

I am in the process of doing several things all at once, and have reached one question I haven’t answered for myself yet. I am a computer repair tech and I have started the process of moving much of what I am doing online onto my wordpress website. I will be accepting paypal, credit card, bitcoin, and one of the items I will sell via woocommerce (that has integrations for Sprout Invoicing and GoURL’s btc integration) are blocks of time.

What I want to do after a client purchases a block of time, is set a timer on the backend that accepts a starting amount of time. I will then start that timer when I begin servicing their issue and when I stop that timer, it shows the client how much of their purchased time is left in their client profile. Perhaps a version of this integrates with woocommerce’s client area so the client sees the purchased time getting reduced there?

However, when I search for countdown timers, all I get are timers to add to public displays of products, pages, or emails. Has anyone created the kind of product-related backend timer I am looking for?