Overfitting is when the model performs well on training data but not on validation data.
We can see from the provided figure that the model is not performing well on the training data itself, which is unlikely due to overfitting.
Based on your training statistics it also looks like you haven’t even completed a single epoch, which may also be the cause of underperforming model as larger datasets often requires multiple epochs.
You can wait for the training to finish and based on the achieved accuracy, try experimenting with different architectures and hyperparameters according to your problem. This may help you in increasing the training accuracy.
The following link can direct you to many resources for CNNs with MATLAB.
Hope this helps.