If all of the bulbs are on the bottom of the Galileo Thermometer the thermometer is too warm. The Galileo may need to be moved out of the direct sunlight and away from heat sources.
If all of the bulbs are floating, the thermometer is too cool. The Galileo may need to be moved away from air conditioning vents or cold windows.
If the bulbs are split between the top and the bottom, the thermometer is working. The lowest of the floating balls in the upper part of the cylinder indicates the correct temperature.