Dissolving is one event, but the energy is easiest to read as three steps. Two cost energy and one pays it back. Pick a salt and watch the three arrows add up to ΔH of solution.
Drag this. Step 3 hands back every bit of it, so the total never moves. Only steps 2 and 3 added together can be measured.
The temperature math uses the measured ΔH of solution, water at 4.18 J/g·°C, and a start of 25.0 °C.