It’s all or nothing. You need to have paid in a total of 85%. If you paid less than 85%, you can’t use this guidance to reduce or eliminate penalty for a quarter in which you were 85% paid. And if you satisfied the 85% total, your penalty for the year is waived, even if you fell short of 85% for some quarters. Quoting the notice, the penalty is waived:
for any individual whose total withholding and estimated tax payments made on or before January 15, 2019, equal or exceed eighty-five percent of the tax shown on that individual’s return for the 2018 taxable year.
This means someone who was way behind in estimated tax payments, incurring penalties for the first three quarters, could have retroactively eliminated those penalties with a large fourth-quarter estimated tax payment. I’m guessing this is why the IRS released this guidance just after January 15.