Ok my knowledge of tax is shaky at best, but this is confusing.

Timeline:

day 1: you buy bitcoin (or mine it and take tax as gross income), bitcoin is valued at $1k USD / bitcoin, you bought 1 bitcoin

day 10: you use the $100 in your debit card to buy many beers, bitcoin is valued at $1.1k USD / bitcoin

day 10 +15 minutes: something sells some of your bitcoin to replenish $100 in your debit card

You now have 10/11th of a bitcoin, valued at $1000 USD, plus $100 of taxable gain for which you probably need to pay the IRS like $15 or something. Or what's wrong in my timeline there?