Clarify that geopoint is number-based (#14)

content/docs/specifications/table-schema.md

@@ -327,11 +327,10 @@ The field contains data describing a geographic point.
 
 `format`:
 
-- **default**: A string of the pattern "lon, lat", where `lon` is the longitude
-  and `lat` is the latitude (note the space is optional after the `,`). E.g. `"90, 45"`.
+- **default**: A string of the pattern "lon, lat", where each value is a number, and `lon` is the longitude and `lat` is the latitude (note the space is optional after the `,`). E.g. `"90.50, 45.50"`.
 - **array**: A JSON array, or a string parsable as a JSON array, of exactly two items, where each item is a number, and the first item is `lon` and the second
-  item is `lat` e.g. `[90, 45]`
-- **object**: A JSON object with exactly two keys, `lat` and `lon` and each value is a number e.g. `{"lon": 90, "lat": 45}`
+  item is `lat` e.g. `[90.50, 45.50]`
+- **object**: A JSON object with exactly two keys, `lat` and `lon` and each value is a number e.g. `{"lon": 90.50, "lat": 45.50}`
 
 #### geojson