Udaya and asta of the grahas
A graha's udaya and asta here follow the Surya Siddhanta (ch. ix): the degrees of time between the Sun's and the graha's crossing of the horizon against the graha's own limit (Guru 11, Shani 15, Mangala 17, Shukra 8 or 10, Budha 12 or 14), read at Ujjain.
Two ways to say a graha is lost in the Sun.
Asta by longitude, as the app's graha cards show it, is while the graha is within its combustion distance of the Sun (BOB-Nakshatra's table, decision 37). The two can differ by days; the pages give both. Vakri runs from the station where a graha's daily motion turns backward to the station where it turns forward, each found to the minute.