Changes for ug add

Author: Wincenttjoi

docs/UserGuide.md

@@ -42,8 +42,6 @@ track of multiple items, OneShelf is for you!
 
 --------------------------------------------------------------------------------------------------------------------
 
-
-
 ## Features
 
 <div markdown="block" class="alert alert-info">
@@ -85,22 +83,29 @@ Alternatives:
 ![Help Summary Screenshot](images/HelpSummaryWindow.png)
 
 
-### Adding an item: `add-i`
+### Adding an item: `add-i` or `add-d`
 
-Adds item to OneShelf, if there's already an item inside with the same name and supplier, it adds on to existing
-quantity of existing item.
+Adds inventory item or pending delivery to OneShelf.
 
 Format: `add-i n/NAME q/QUANTITY [s/SUPPLIER] [max/MAX_QUANTITY] [t/TAG]...​`
+* Adds `QUANTITY` from the current quantity of an inventory item if the item already exist.
+An item is uniquely identified by its NAME and SUPPLIER.
 
-<div markdown="span" class="alert alert-primary">:bulb: **Tip:**
-A item can have any number of tags (including 0)
-</div>
+Examples: `add-i n/CHICKEN q/10 s/NTUC max/50`
 
-### Adding a delivery: `add-d`
+Assuming that your inventory item is empty, entering the above command would add a new chicken item that was previously purchased from NTUC. <br>
+By entering `add-i n/CHICKEN q/10 max/50`, a new inventory item would be added instead of increasing the quantity since the second chicken has no supplier. <br>
+On the other hand, by entering `add-i n/CHICKEN q/10 s/NTUC` again would increase the quantity of Chicken from NTUC to be 20kg.
 
-Adds delivery to OneShelf
 
-Format: `add-d n/NAME, p/PHONE, a/ADDRESS, o/ORDER`
+Format: `add-d n/NAME p/PHONE a/ADDRESS o/ORDER`
+
+Examples: `add-d n/DAMITH p/91111111 a/Blk 251 Orchard Road o/Nasi goreng x1`
+
+<div markdown="span" class="alert alert-primary">:bulb: **Tip:**
+* An item can have any number of tags (including 0)
+* Unlike inventory item, pending delivery does not have a quantity.
+</div>
 
 ### Removing quantity from an item: `remove-i`