Cheat Engine

[Mahi]

I'm trying to create a trainer for Duke Nukem: Manhattan Project, but I ran into a problem: some of the values/addresses (f.e. ammo) appear to be both Byte and 2 Bytes? I'm really new to CE and memory hacking etc. so try and bare with me.
If I do a search with "Value Type: All" and keep rescanning with different ammo values, I will find the following addresses:

[vergilganesh]

Try using pointerscan. Make a google search about pointerscan.

[smx]

02A6C4CC is both 1 and 2 bytes, because the size of the address is 2 bytes, but it can also contain a byte.

CE's is telling you that because at
09F6D721 - 66 89 01 - mov [ecx],ax <<

ax is involved.
ax is a 16 bits register, which means it can contain 2 bytes (16/8 -- 8 bits = 1 byte)
In this case, it's holding the value 68 (EAX=00000068), and 68 is 1 byte (here's why the double address)
68 in hex == 104 in dec

About the Hex Scanning, i don't think you need it in this moment, because there is no offset.
Pointer scanner use is when you have, instead of your instruction:
mov [eax*4+esi],ax or something similar, so you want to know where is [eax*4+esi], and you do a pointer scan to find the address.

The instruction mov [ecx],ax means:
Take the value that is stored in the ax register (our ammo), and copy that value to the address contained in ecx.
This means that this instruction updates ammo at 02A6C4CC (and you already have it in your table).

If you want to change ammo without auto-assembler, you should backtrace ax (your ammo), to see where some value is put into it. You could click on Show Disassembler, then Tools, Dissect Code, and then scroll up to find where an opcode like this:
mov ax,[something]
occurs

You should be able to find the piece of code which loads ammo from an address into memory. Then you can see if it that address is static or a pointer (which needs pointer scanning).