"Somewhere" is not a reliable source for tax information.
The California tax rates are the same for residents and nonresidents. It's not a single fixed rate. It's a sliding scale, like federal tax rates, and the rates depend on your filing status and income. The brackets range from 1% to 12.3%. You can see the Tax Rate Schedules at the following link, or see below for a PDF.
2019 California Tax Rate Schedules
The "line to exceed" for filing a California nonresident tax return depends on your filing status, age, and number of dependents. See the chart at the link in my first reply above, or the PDF below.
The charts for the filing requirements and the Tax Rate Schedules might be easier to read in the PDF of the Form 540NR instructions. You can download it from the following link. The filing requirements are on page 3 and the Tax Rate Schedules are on page 92.
Form 540NR Booklet
