There is a left PCA occlusion. When assessing the cerebral vasculuture, make sure you focus on the posterior circulation. The cerebral veins (basal vein of rosenthal) travel close to the PCA, so ensure that you don't accidentally follow a venous structure instead of the PCA.
The often quoted ideal stroke windows are 35 35 , or 40 40. But it is suggested to always window and level yourself based on your visual preferences. Many factors such as monitor grey scale values can affect the final output, so better to rely on a window and level that is comfortable for you in detecting the subtle grey-white differentiation.