I don't know about end of sehri time in your place and why there are two different times. Maybe 4.16 is imsaq and 4.24 is subh. Maybe both are imsaq, or maybe both are subh.
My advice. Until you get an information from local alim, it's better if you stop sehri at 4.16. This is the safer option.
Q: As I am fasting I thought the last time for sehri was 3:50am (mistakenly) but the actual last time for sehri was 3:49am. I drank water at 3:50am sharp. Would my fast be valid?
:bism:
A: As a precaution keep one qadha. And Allah Ta'ala (الله تعالى) knows best.