How to use a good use of nb_train_samples in keras?
Yes, they have to be the same.  These are the parameters you use to tell the process how many you have of each type of image.  For instance, if you tell it that you have 5_000 validation samples, but there are only 3_000 in the data set, you will crash the run.
I'm using keras with Tensorflow-gpu backend in Python. I'm trying to put the correct number of nb_train_samplesn nb_validation_ samples and epochs.
I am using the fit-generator-method.

nb_train_samples has to be the same number that images that i have for training? Can be higher?
nb_validation_samples has to be the same number that images that i have for validation? Can be higher?