Solid line = floor (spellings that unambiguously belong to the group). Shaded band up to the dashed edge = ceiling (the most it could reach if every ambiguous spelling counted here).
Tina was a common American name in the 1960s but is rarely given today. It's been given to 306,982 U.S. babies all time and once ranked 237th by sound, peaking at 15,149 in 1968 (down to 66 in 2025).
By sound, Tina also includes the spellings Tena, Teena.
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).