Update NumericUnits.md

added guide for evaluation function parameters

Author: CarkHT

docs/teacher/reference/response_area_components/NumericUnits.md

@@ -2,21 +2,34 @@
 
 Provides two input fields with `Number` and `Units` placeholder texts. This area will also display its associated grading function (as seen in the screenshot below). 
 
-**Note** this area will display how the user's response was interpred using the `interp_string` field provided in the feedback object returned by that function (if it exists).
+**Note:** this area will display how the user's response was interpred using the `interp_string` field provided in the feedback object returned by that function (if it exists).
 
 ## Component Parameters 
-### `pre_response_text` (optional)
-Text block to be displayed to the left of the input field. Markdown and LaTeX are allowed following the usual syntax.
+### `pre_response_text` & `post_response_text` (optional)
+Text block to be displayed to the left and right of the input field respectively. Markdown and LaTeX are allowed following the usual syntax.
+### Comparing units
+By ticking the `physical_quantity (boolean)` option in the *Evaluate* tab, answers with different units from the reference answer can be compared.
+
+![physical quantity ticked](screenshots/physical_quantity.png)
+
+For example, if the reference answer is 100 m, the following answers will also be accepted:
+
+*   0.1 km
+*   10000 cm
+*   10^5 mm
+### Tolerances
+Tolerances can be added to your answer using the `atol (number)` and `rtol (number)` fields, which denote absolute and relative tolerances respectively.
 
 ## Response Structure
 *This is how the react component will structure the user's input to the Grading Gateway, when they press the check button.* 
 
 In this case, the response is a single string which features the user's response to both fields separated by a space.
+
 !!! example 
 
     ```json 
     "response": "150 g"
     ```
 
 ## Example Screenshot 
-![Screenshot](screenshots/NumericUnits.jpg)
+![Screenshot](screenshots/NumericUnits.jpg)