Exchange overrounds advice

[A Former User]

When i watch the horse markets an hour or so before the off i see overrounds on the exchange that are miles apart from the last 20 min,

Often it is one horses price that causes this, sometimes two and i sit a ponder which way the odds will move to tighten the overround 10 100%ish - it also tends to be the lay overround that tends to be about 90% when im looking. Is there anything i can do to get a good idea of which way that horses odd will move in order to tighten up?