I dont understand !!!

Share something here

Cny 2010
The sister is jx gratuade frm Uni n bcm a degree holder
found job

buy lots Cny staff for her younger bro
its worth RM300

one day:
bro ask her to dabao somethng to him
the food worth onli a RM5
but she take frm him still
bro gv a RM10
n sis nv gv him back the other RM5 tht b left over
after 3days
bro ask for the RM5 again
thn she said: i think u should gv me back a RM 295 lo

huh?
wat this mean?
i dun understand
is this mean the sister can always use this RM300 to order her bro?
my answer: NO!!!
but she really did~