The compound shown is 4-methylhepta-2,5-diene drawn without stereochemistry. Counting geometrical and optical isomers together, the total number of stereoisomers is

Both double bonds can be $E$ or $Z$. When the two double bonds have the same geometry, $(E,E)$ or $(Z,Z)$, C4 carries two identical propenyl groups and is not a stereocentre, giving 1 achiral compound each: 2. When the geometries differ, $(E,Z)$, C4 carries two different groups and becomes a stereocentre, giving a pair of enantiomers: 2. The naive count $2\times 2\times 2=8$ is wrong because of the symmetry. Total: $2+2=4$.