diff -r QGIS/resources/function_help/json/$x_at QGIS_edit/resources/function_help/json/$x_at
5c5
<   "arguments": [ {"arg":"i","description":"index of point of a line (indices start at 0; negative values apply from the last index)"}],
---
>   "arguments": [ {"arg":"i","description":"index of point of a line (indices start at 0; negative values apply from the last index, starting at -1)"}],
diff -r QGIS/resources/function_help/json/$y_at QGIS_edit/resources/function_help/json/$y_at
5c5
<   "arguments": [ {"arg":"i","description":"index of point of a line (indices start at 0; negative values apply from the last index)"}],
---
>   "arguments": [ {"arg":"i","description":"index of point of a line (indices start at 0; negative values apply from the last index, starting at -1)"}],