Three other PNGs in the same thread >>121 have the iDOT chunk. They all follow the same structure rules explained above.
AJlNWhC.png
0 0x00000008 13 b'IHDR' 0x7447CAAA
1 0x00000021 1 b'sRGB' 0xAECE1CE9
2 0x0000002E 28 b'iDOT' 0x7EA8BF4F
3 0x00000056 16384 b'IDAT' 0x67E3CD1F
4 0x00004062 16384 b'IDAT' 0x7C47A125
5 0x0000806E 16384 b'IDAT' 0x5B75E165
6 0x0000C07A 7512 b'IDAT' 0xCD0D8D01
7 0x0000DDDE 16384 b'IDAT' 0x632D36D0
8 0x00011DEA 16384 b'IDAT' 0x0D987BA8
9 0x00015DF6 3045 b'IDAT' 0x7E530BF5
10 0x000169E7 0 b'IEND' 0xAE426082
00000000 89 50 4e 47 0d 0a 1a 0a 00 00 00 0d 49 48 44 52 |.PNG........IHDR|
00000010 00 00 06 44 00 00 04 d6 08 06 00 00 00 74 47 ca |...D.........tG.|
00000020 aa 00 00 00 01 73 52 47 42 00 ae ce 1c e9 00 00 |.....sRGB.......|
00000030 00 1c 69 44 4f 54 00 00 00 02 00 00 00 00 00 00 |..iDOT..........|
00000040 02 6b 00 00 00 28 00 00 02 6b 00 00 02 6b 00 00 |.k...(...k...k..|
00000050 dd b0 7e a8 bf 4f 00 00 40 00 49 44 41 54 78 01 |..~..O..@.IDATx.|
00000060 ec dd 07 78 1c c5 f9 c7 f1 57 b6 dc 7b 53 71 b7 |...x.....W..{Sq.|
hLzyLXE.png
0 0x00000008 13 b'IHDR' 0x952CDFFB
1 0x00000021 1 b'sRGB' 0xAECE1CE9
2 0x0000002E 28 b'iDOT' 0x06937509
3 0x00000056 16384 b'IDAT' 0xF8A0C4FE
4 0x00004062 16384 b'IDAT' 0xA6CBEFA6
5 0x0000806E 16384 b'IDAT' 0x8F56E791
6 0x0000C07A 14545 b'IDAT' 0x1AFB96B3
7 0x0000F957 16384 b'IDAT' 0x171F7142
8 0x00013963 16384 b'IDAT' 0xDDA443B1
9 0x0001796F 15708 b'IDAT' 0x5C976470
10 0x0001B6D7 0 b'IEND' 0xAE426082
00000000 89 50 4e 47 0d 0a 1a 0a 00 00 00 0d 49 48 44 52 |.PNG........IHDR|
00000010 00 00 06 3e 00 00 04 d6 08 06 00 00 00 95 2c df |...>..........,.|
00000020 fb 00 00 00 01 73 52 47 42 00 ae ce 1c e9 00 00 |.....sRGB.......|
00000030 00 1c 69 44 4f 54 00 00 00 02 00 00 00 00 00 00 |..iDOT..........|
00000040 02 6b 00 00 00 28 00 00 02 6b 00 00 02 6b 00 00 |.k...(...k...k..|
00000050 f9 29 06 93 75 09 00 00 40 00 49 44 41 54 78 01 |.)..u...@.IDATx.|
00000060 ec dd 07 9c 5c 55 dd ff f1 df 26 9b de 2b 84 74 |....\U....&..+.t|
Vc2eT5I.png
0 0x00000008 13 b'IHDR' 0xBDCA725C
1 0x00000021 1 b'sRGB' 0xAECE1CE9
2 0x0000002E 28 b'iDOT' 0x81ED3D30
3 0x00000056 16384 b'IDAT' 0xE92A8FA4
4 0x00004062 1762 b'IDAT' 0xBCDA142D
5 0x00004750 16245 b'IDAT' 0xE624764B
6 0x000086D1 0 b'IEND' 0xAE426082
00000000 89 50 4e 47 0d 0a 1a 0a 00 00 00 0d 49 48 44 52 |.PNG........IHDR|
00000010 00 00 02 00 00 00 02 32 08 06 00 00 00 bd ca 72 |.......2.......r|
00000020 5c 00 00 00 01 73 52 47 42 00 ae ce 1c e9 00 00 |\....sRGB.......|
00000030 00 1c 69 44 4f 54 00 00 00 02 00 00 00 00 00 00 |..iDOT..........|
00000040 01 19 00 00 00 28 00 00 01 19 00 00 01 19 00 00 |.....(..........|
00000050 47 22 81 ed 3d 30 00 00 40 00 49 44 41 54 78 01 |G"..=0..@.IDATx.|
00000060 ec 9d 07 9c 1c 65 f9 c7 9f bd 9a 2b b9 e4 72 b9 |.....e.....+..r.|