What is happening here??? ("multiple input files are writing to...")

[drakonicguy]

I'm getting this error...

[11ty] Output conflict: multiple input files are writing to `_site/blog/index.html`. Use distinct `permalink` values to resolve this conflict.
[11ty]   1. ./help.html
[11ty]   2. ./help.html
[11ty]   3. ./help.html (via DuplicatePermalinkOutputError)

It says that multiple input files are writing to the same permalink.. While listing ONE input file.

[drakonicguy]

UPDATE: I'm a dummy and I forgot about pagination.

I set this as the permalink and everything works nicely now:
permalink: "/blog/{% if pagination.pageNumber > 0 %}{{ pagination.pageNumber}}/{% endif %}/"