You have to explain what kind of system was calculated and how the calculation has been done.
For such figure of band structure, you cannot figure out the band gap value because at the Fermi level there is a very flat band. If your calculated system contains defect or impurity, your calculated band structure plot may indicate that the Fermi level is pinned at the defect level. If no defect or impurity is included, it may indicate that you have to perform the spin-polarized calculations.
