validation path and valid data

[twinklecc]

Hi, after preprocess of dataset, I have got the extracted mels in my assigned mel-path.
But for next running of trainner.py, there should be proper validation path as the 3rd line in config:
validation: 'H:\Deepsync\backup\deepsync\LJSpeech-1.1\valid'
I am confused of which part of data should I put in this valid path, the paired mels and wavs for validation?
Since you have designated the LJ/wavs as the train data path, then how to split the data as training part and validation part?
Looking forward to your reply and very thanks!