If Ashwini is the star which is owned by Ketu, the first sub lord in Ashwini star will be Ketu, the second sub lord will be Venus, the third sub lord will be of Sun and so on.
If Bharani is the star which is owned by Venus, the first sub lord in Bharani star will be Venus, the second sub lord will of Sun, the third sub lord will be of Moon and so on.
You can notice that there is no name given to a sub like we have given the names for signs and stars. What we are mostly cocerned about is the lord of that sub i.e. sub lord.
The span of a sub lord can be calculated as follows -
Span of a Sub Lord = (Years of Planet in Vimshottari Dasa/ 120) X 13 degree 20 minutes
as 13 degree 20 minutes can also be written as 800 (13 X 60 + 20) minutes, for simplicity of calculation, we can say -
Span of a Sub Lord (in minutes) = (Years of Planet in Vimshottari Dasa/ 120) X 800
based on this we can calculate the span of each sub lord as follows -
Span of a Sub Lord Ketu = (7 / 120) X 800 = 46.6666 = 0 degree 46 minutes 40 seconds
Span of a Sub Lord Venus = (20 / 120) X 800 = 133.3333 = 2 degree 13 minutes 20 seconds
Span of a Sub Lord Sun = (6 / 120) X 800 = 40 = 0 degree 40 minutes 00 seconds
Span of a Sub Lord Moon = (10 / 120) X 800 = 66.6666 = 1 degree 6 minutes 40 seconds
Span of a Sub Lord Mars = (7 / 120) X 800 = 46.6666 = 0 degree 46 minutes 40 seconds
Span of a Sub Lord Rahu = (18 / 120) X 800 = 120 = 2 degree 0 minutes 0 seconds
Span of a Sub Lord Jupiter = (16 / 120) X 800 = 106.6666 = 1 degree 46 minutes 40 seconds
Span of a Sub Lord Saturn = (19 / 120) X 800 = 126.6666 = 2 degree 6 minutes 40 seconds
Span of a Sub Lord Mercury = (17 / 120) X 800 = 113.3333 = 1 degree 53 minutes 20 seconds