Hi

I I have Dell Inspiron 15R 5520 it has come with a memory Hynix 4GB As shown in the picture

And I want to add a new 4GB memory to be 8GB 

 

I searched in amazon for the same type

And I found two, but they don't match in the last two numbers. I've marked the part in red that doesn't match

My questions

What does this last part of the numbers mean?

And if I buy one, it will be identical to the old memory and will work without problems?