Is it obligatory to give the poor person the entire agreed-upon amount for marriage assistance, or is it sufficient to pay the initially determined amount, knowing that the intention has secretly changed to increase the amount?

The statement of a person to himself, "I will give so-and-so such-and-such," entails nothing but the reward for a good intention, based on the saying of the Prophet, peace and blessings be upon him: "Whoever intended to perform a good deed, but did not do it, Allah records it for him as a complete good deed." However, if he said aloud, "I will give so-and-so such-and-such," and it was not a vow, then he is not obligated to anything, and he is rewarded for his resolve. As for his promise to a person to buy a bedroom set, he is required to fulfill the promise, either obligatorily or commendably, depending on the situation of the promised person.