Error in Movements

Hi,

I am trying to post the goods movement and i am getting two kinds of errors.

1) Deficit of SL Unrestr. prev. 1 EA : 24543255161 BP01 B884

2) Deficit of SL Unrestricted-use 1 EA : 24543255161 BP01 A259

The 2nd error is the deficit of stock in storage location in A259. But what's the difference between these two errors is my question. Could some one please tell me the difference.

Thanks.