The problems begin with the multiple sparks from the MSD. The digital 6, 7 and the DIS can be the worst. Ironically old timing lights seem to work because they just aren't fast enough to see the extra pulses. Some newer dial-back lights can see the extra pulses and get confused. The MSD timing lights are specifically designed to handle this.

But if you get a stable timing reading with the light you have, you're OK as-is. As you pick up in RPM you may start to see some jittering and some dial-backs just flat stop flashing.

If you get a good flash, it's not an accuracy issue. If you decide to buy a new timing light, make sure the specs say it can handle DIS ignition.