The wording 19 O’clock is a little off - technically and in everyday usage - it would either be 7 O’clock or, if you want to write it out in full, 19 hundred hours. 7 O’clock is better for this sentence, if you want to be sure there’s no confusion you can just add pm. O’clock is a shortened form of the original ‘of the clock’, and as the clock face has only numbers 1-12 that’s why it sounds a little off.