Problem with storage write to pos 0

this is interesting

>st.write("f",'',0,10)
=true
>st.read('f')
="\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF"
>st.write("f",new Uint8Array([3,4]),2,10)
=true
>st.read('f')
="\xFF\xFF\3\4\xFF\xFF\xFF\xFF\xFF\xFF"
>st.write("f",new Uint8Array([5,6]),4,10)
=true
>st.read('f')
="\xFF\xFF\3\4\5\6\xFF\xFF\xFF\xFF"
>st.write("f",new Uint8Array([1]),1,10)
=true
>st.read('f')
="\xFF\1\3\4\5\6\xFF\xFF\xFF\xFF"
>st.write("f",new Uint8Array([0]),0,10)
=true
>st.read('f')
="\0\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF"

you can write to different location and give total size in each call and data stays, you can even write to position 3,4 then 5,6 and then to 1(!, nice) but if you write to position 0 new file is created and rest is filled with \xFF