The article said "researchers at The University of Texas at Austin and Texas A&M University have developed an electronic tattoo that,..., and deliver continuous blood pressure measurements at an accuracy level exceeding nearly all available options on the market today".
“0.2 ± 4.5 mm Hg for diastolic pressures and 0.2 ± 5.8 mm Hg for systolic pressures, a performance equivalent to Grade A classification” per the Nature abstract linked in the article: https://www.nature.com/articles/s41565-022-01145-w
But yeah they didn't dive into specifics.