The content IDs seem to skip over some numbers or do not start from 1. What is the counting logic behind them?

Content IDs are assigned in the order of creation.

IDs not starting from 1

Kuroco creates new sites by copying existing ones. For this reason, the content ID may not start counting from 1.

Skipped numbers

IDs are counted in increasing numerical order across all content structures. Therefore, within each content structure, the IDs may appear to skip over some numbers.

Also, if one piece of content (B) is created and saved while another piece (A) is still in progress, the ID for B will skip over the ID assigned to A.