the problem of my circuit is jumping counts. I checked several times already . The stimulation is good . It will start as 0 and increase digit 1 by 1 . it has same result as down counter which is decreasing 1 by 1. However, it is totally different when coming to pcb board and breadboard. After i done the circuit, i tried at breadboard and found out there are few problems occurred . First, it will start with 999 after power supply is connected. Come to the counter up and down , it will keep jumping . I tried switch debouncer too and it is the same result. Currently , i am still check the problem and found out Q0 from 74ls192 will keep on no matter button for up or down. Below there shows the general design and detailed image for connections from proteus . This design on pcb already cost me for 2 weeks and still cant get the solution.