What's with the time travelling delay in The Time Machine by H.G.Wells?

I recently got The Time Machine by H.G.Wells and I am quite intrigued by this line near the end of the story :-

"But is it not some hoax?" I said. "Do you really travel through time?"

"Really and truly I do." And he looked frankly into my eyes.
He hesitated. His eye wandered about the room. "I only want half an
hour," he said. "I know why you came, and it’s awfully good of you.
There’s some magazines here. If you’ll stop to lunch I’ll prove you this
time travelling up to the hilt, specimens and all. If you’ll forgive
my leaving you now?"

In the paragraph above, I have highlighted the words – "half an hour" – as I am slightly confused by the fact that even though he had the power to travel to any point in time he wanted, he asked for half an hour of time. He could have just time travelled, obtained his specimens, and returned with them moments later, although in reality, he would have travelled to the future and back again.

Why does he ask for such a long time here? Was he trying to prevent a paradox? He did not need to get ready or anything, because the author briefly left and then returned almost immediately to tell the Time Traveller that he had an appointment, and the Time Traveller had already departed.

Why did he ask for so much time?