What is the meaning of the phrase: "From this it is understood that if the choice explicitly mentioned divorce, then divorce would certainly occur," which appears in the context of discussing giving the wife the choice [to divorce]?

If a husband gives his wife a choice [regarding divorce] and intends divorce, and she responds with an explicit phrase like "I divorce myself," then her divorce takes effect by that, regardless of her intention. This is because an explicit verbalization does not require an intention, unlike an ambiguous one.