How does the diffusers progress bar work?

Question

I'm upscaling an image using StableDiffusionUpscalePipeline, but the second timestamp does not appear to be total estimated duration after all. What is it then and how to get a useful estimate?

Loading pipeline components...: 100%|█████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 6/6 [00:01<00:00,  3.62it/s] 
 52%|███████████████████████████████████████████████████████████████████████████▉                                                                      | 39/75 [4:26:46<4:19:26, 432.40s/it]

tqdm uses smart algorithms to predict the remaining time and to skip unnecessary iteration displays, which allows for a negligible overhead in most cases.

I'll have to dive into that code and see if there's a more conservative estimate, but there's probably an expert here who's already done that.

Answer 1

 55%|███████████████████████████████████████████████████████████████████████████████▊                                                                  | 41/75 [4:41:20<4:06:17, 434.63s/it] 

It's "time spent < time left". I feel mildly embarrassed.