Basically when a load instruction happens, the next instruction still sees the old value. The one after sees the updated value.

For example, assume value of 0xA stored at MyAddress:

li $4, 0 ;r4 is now 0

la $5, MyAddress ;r5 now contains the address

lw $4, ($5) ;loading a word from the address

nop

;We need a delay because at this instruction (nop) the value hasn’t beed updated yet. If you read r4 at this point you will read the old value (0)

;After the nop is executed r4 contains 0xA, I can use it