if the value of heat, q, is positive when the temperature of a sample of water changes, then

If the value of heat, qqq, is positive when the temperature of a sample of water changes, then the temperature of the water was increased. This means that heat has flowed into the water from the surroundings, causing the water to absorb heat and increase its temperature. This is because a positive qqq corresponds to heat absorbed by the system (water in this case), resulting in a temperature rise. Conversely, if qqq were negative, it would indicate heat released by the water and a temperature decrease.