For this topic, my understanding is that two-thirds of 24 senators is 16 votes.
The Philippine Constitution says that no person can be convicted in an impeachment trial without the concurrence of two-thirds of all the Members of the Senate.
So, my answer to the second question is No, not automatically.
If four senators are unable to participate, the Senate does not automatically become a 20-member Senate for purposes of calculating the constitutional threshold. The key question is how the phrase “two-thirds of all the Members of the Senate” should legally be interpreted.
That is why the issue has been referred to legal experts, and there are differing interpretations: some argue for calculating based on the senators able to participate, while another interpretation maintains that the full Senate membership remains the constitutional basis.
So, in my view, 16 is the straightforward calculation from 24, while reducing it to 14 requires a legal basis—not simply the fact that four senators cannot vote.