Why the water temperature matters
Hot water pulls more bitterness out of delicate leaves. The Tea Association of the USA recommends about 160 to 180°F for green tea and about 185°F for white, while black tea takes water at or just under a full boil. That is why the line under the buttons gives a temperature for every type and not only a time.
The Association gives ranges, such as 3 to 5 minutes for black tea.
The Association gives ranges, such as 3 to 5 minutes for black tea. The timer uses one number inside each range: 2 minutes for green (range 1 to 3), 3:30 for white (3 to 4), 4 for oolong (3 to 5) and 4 for black (3 to 5). Taste a cup, then use the shorter end for a lighter tea and the longer end for a stronger one.
Herbal tea
The Tea Association figures cover true teas, so herbal comes from a brand instead. Celestial Seasonings says to pour freshly boiled water over one tea bag and steep 4 to 6 minutes, and the timer uses 5. Blends with roots, bark or large pieces of fruit may taste better with a longer steep, so check the box.
Where these times come from
Black (3 to 5 minutes at 201 to 210°F), oolong (3 to 5 minutes at 175 to 195°F), white (3 to 4 minutes at about 185°F) and green (Chinese green 1 to 3 minutes at 170 to 180°F, Japanese green 1 to 2 minutes at 160 to 175°F) are the Tea Association of the USA's recommendations as reproduced at https://resource.bunn.com/library/eZine/tea_basics_brochure/files/basic-html/page3.html. Herbal (4 to 6 minutes, freshly boiled water): Celestial Seasonings, Brewing Methods, https://celestialseasonings.com/pages/brewing-methods. Many consumer guides give different numbers, for example longer steeps for white tea. We used the Association's figures because it is the trade body for tea in the United States. The green preset is 175°F, the overlap between its Chinese and Japanese ranges.