See inventoryn.png

"The red box shows the character loaded. In this case, it is Ada default.

The light green box is our first weapon entry. The first two bytes define the weapon. 01 0C = Ammo Box 50. The third byte defines how much ammo is loaded in the secondary mode (example: Ada's pipe bomb arrows, Bear Commander grenades, Leon's second pistol). But her machine pistol doesn't have a secondary ammo so it is left as 00. The fourth byte defines how much ammo is loaded into the primary clip. Ada's machine pistol has 50 bullets from the start. 32 in hex = 50 in decimal.

NOTE: For weapons like knives/Stunrods/Hand-to-hand the last two bytes are left as FF.

After that we see she has her crossbow with one normal arrow loaded into it. 

The dark brown box shows an empty slot for any weapon you want to load in it, same format as the first two before it. So in total you can have up to seven weapons at a time!

The light brown box is your Herb Case. The amount of herbs already in the case is defined by the last byte, so in Ada's case she has 8 herb tablets.

The values between the herb case and the grey box are only for the quick grenade menu. Giving them a quantity does nothing as the amount of grenades and First Aid sprays are stored in your Ammo menu.

The beginning of our ammo menu begins with the grey box. Again, the first two values define the item, and the last value defines the amount, so in all Ada has three flame grenades!

In all you have 9 slots for your ammo/grenade menu. 

Hope this helps!

EDIT 2: Using the above method I managed to get Pier's arm working for mercenaries. 

Input his arm as 01 26 00 00. Anyone can use it."