Why does Matthew Pocket tell Pip he isn’t “an alarming personage”? What is Pip’s impression of Matthew?

Mr. Pocket is letting Pip know that he isn't a scary man.... Pip believed him to be genuine and natural.

Mr. Pocket said he was glad to see me, and he hoped I was not sorry to see him. “For, I really am not,” he added, with his son’s smile, “an alarming personage.” He was a young-looking man, in spite of his perplexities and his very gray hair, and his manner seemed quite natural. I use the word natural, in the sense of its being unaffected; there was something comic in his distraught way, as though it would have been downright ludicrous but for his own perception that it was very near being so.