About Samuel, because Scripture does not explicitly assign a number of years to him, I think that the length of Saul's reign which is mentioned by the holy Apostle should belong jointly to Saul and to Samuel.
It is clear that Samuel was leader of the people for many years; but Scripture states that Saul reigned for just two years.
In the first book of Kings, it says [ 1 Samuel, 13'1 ]: “Saul was the son of a year in his reigning; and he ruled over Israel for two years".
Symmachus makes this clearer in his translation: “Saul was like a year-old child in his reigning", meaning that Saul was pure and faultless at the beginning of his reign.
He kept that nature for two years, but when he turned to evil ways, he was rejected by God and suffered divine punishment.
Therefore the remaining years have been assigned to Samuel, and 40 years is the joint total for Saul and Samuel.
It is clear that Saul [or Samuel] ruled for this length of time, not only from the evidence of the Apostle, but also from a careful investigation of Scripture, which says [ 2 Samuel, 2'10 ] that after the death of Saul, “Ish-Bostheth son of Saul was 40 years old when he became king over Israel, and he reigned two years.
The house of Judah, however, followed David.” Ish-Bostheth must have been born after Saul became king, because Scripture [ 1 Samuel, 14'49 ], when talking of the beginning of Saul's reign, mentions three sons of Saul, but not this one.
Therefore we think that Ish-Bosheth was born later, and the length of Saul's reign was about the same as the age of his son after his death.