Contour lines reading in the negatives?

Just curious I’ve been experimenting with a map I made and I wanted to see how the contour feature would come out. Everything came out nice expect when I click on a line the elevation will read in negative numbers. Its identifying hills areas but its not reading a correct topo. For example highest part of the hill reads -30m while the bottom is reading -37m . According to a local topo map the top part of the hill should be at 150 Feet which is about 48m.