Track your daily writing streak.
A writing streak works because the daily minimum is low enough to be unmissable, which is the entire point — 300 words is fifteen minutes on a bad day, so there is no honest excuse to break the chain. Allowing planned rest days is what makes a streak survivable long term: a streak requiring all seven days breaks at the first illness or family commitment and rarely restarts. Counting writing days separately from calendar days reflects that. The cumulative word total at the goal is the figure worth looking at, because 60 days at 300 words is 18,000 words — the point of the habit rather than the number itself.
Days to goal
Writing days = goal streak - current streak
Calendar time
Calendar days = writing days x 7 / (7 - allowed rest days)
No — deliberately low. The purpose of a streak is consistency, not volume, and a minimum you can hit on your worst day is what keeps the chain intact. Three hundred words is achievable when tired or busy; 2000 is not, and a missed day usually ends the streak for good.
Only if you define them that way. Building planned rest days into the rule is what makes long streaks survivable — otherwise the first illness or family emergency ends it. The habit you want is regular writing, not literally uninterrupted writing.