Defined as the Hour Angle, Hora Kona, of the Vernal Equinox, by the mighty West and as Sayana Ravi Madhyam in minutes by India, S T is the major factor in Lagna Sphuta Ganitha, for computing the Ascending Degree, the first computational Point in House Division.
My Sun at 90 degrees means 90^ 4 = 360 mins of Sidereal Time.
In Indian Lagna Sphuta Ganitam, it is always Udayal Param or After Sunrise. So the Mean Sun is accounted for.