Naming series auto increment issue

Hi,

I have created a series list in Sales Order, the list are BJAP.YY.MM.### and VJAP.YY.MM.###, the naming series does not auto increment.

for example:
BJAP.YY.MM.2106001 will be my first order
VJAP.YY.MM.2106001 again the second order will be of same sequence
BJAP.YY.MM.2106002 for next order

Please help me to find how to increment the each order as below:
BJAP.YY.MM.2106001
VJAP.YY.MM.2106002
BJAP.YY.MM.2106003
VJAP.YY.MM.2106004

Thank you,
Vishnu