Minor clarification of when to use > vs >= in incremental models (#…

…3714)

## What are you changing in this pull request and why?
Fixes #2606

## Checklist
- [x] Review the [Content style
guide](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/content-style-guide.md)
and [About
versioning](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/single-sourcing-content.md#adding-a-new-version)
so my content adheres to these guidelines.
- [x] Add a checklist item for anything that needs to happen before this
PR is merged, such as "needs technical review" or "change base branch."

website/docs/docs/build/incremental-models.md

@@ -57,6 +57,7 @@ from raw_app_data.events
 {% if is_incremental() %}
 
   -- this filter will only be applied on an incremental run
+  -- (uses > to include records whose timestamp occurred since the last run of this model)
   where event_time > (select max(event_time) from {{ this }})
 
 {% endif %}
@@ -137,6 +138,7 @@ from raw_app_data.events
 {% if is_incremental() %}
 
   -- this filter will only be applied on an incremental run
+  -- (uses >= to include records arriving later on the same day as the last run of this model)
   where date_day >= (select max(date_day) from {{ this }})
 
 {% endif %}