accounting!请教关于End-Of-Period Adjusting Entries

xx supplies expense 800
xx supplies 800
(to record xx sup. used)
and the genera ledger:(take this month for e.)
xx sup.
-----------------------
1/14 1200| 1/31 400
-------------|
1/31 bal.800|
xx sup. expense
-----------------------
1/31 adj.400|
p.s.我也是初学者