Thank you slowsmile. Human communication is tough at times...
Let me count sequentially (i.e. reading from top to bottom), plugin-wise:
001, 010, 011, 012, 013, 014, 015, 016, 017, 018*, 002, 003, 004, 005, 006, 007, 008, 009
To compare with Sigil
001, 002, 003, 004, 005, 006, 007, 008, 009, 010, 011, 012, 013, 014, 015, 016, 017, 018*
*The book contains 18 images so there is no 019.
Take the first number (three digits) of each of these two lists above which is the same 001 (luck!). The number following immediately this number 001 (I mean on its right) is NOT the same for the plugin than for Sigil. One of them may be wrong.