If the glass is located upright, the height of water is about 5 cm because the height of glass is 10 cm and it is partially filled with water and we know that partial means 50 percent of something and here 50 percent of glass is 5 cm. If the glass is slightly bend, so we can't find its right height so the proper height of water is attain if it is placed on flat table and present upright.
Significant digits (also called significant figures or “sig figs” for short) indicate the precision of a measurement. A number with more significant digits is more precise. For example, 8.00 cm is more precise than 8.0 cm.
