I'm not entirely sure this is the right community for this question but it doesn't seem to fit anywhere else. I also don't see any similar questions.
I've included the DropBox links because they're too large for Imgur or other free hosting sites. The first is 10,830 × 4,981 PNG (53.9 megapixels) and 2,400,601 bytes (2.3 megabytes). The second is 10,812 × 5,159 PNG (55.8 megapixels) and 16,451,853 bytes (15.7 megabytes). They have identical information from Jeffrey Friedl's tool.
PNG Animation no Bit Depth 8 Color Type RGB with Alpha Compression Deflate/Inflate Filter Adaptive Image Size 10,830 × 4,981 Interlace Noninterlaced Gamma 1.7362 Profile Name Photoshop ICC profile Pixels Per Unit X 3,780 Pixels Per Unit Y 3,780 Pixel Units meters
Can anyone explain why the two file sizes are so different despite being similar or identical in every other way? I haven't been able to find an answer anywhere else, although that might be because of my inability to phrase the question correctly or use the right terminology.