"netting" means to combine cash inflows and outflows (e.g. debits/credits, payments/receipts, income/expense) by subtracting the sum of all outflows from the sum of all inflows, creating one transaction.
For example, if you make two trades in one day with your broker - one to buy a security for $100 and one to sell it for $110 - rather then you sending your broker $100 and them sending you $110, the transactions are "netted" - meaning they will send you the "net" amount of $10 ($110 inflow - $100 outflow).
In a more general sense ("netting of instructions") it would mean to combine all instructions and only apply the "net" effect - e.g. one step forward, two steps back would combine to a "net" one step back. Most likely it will apply to the exchange of money, but it could be applied more broadly.
Note that there doesn't have to be both inflows and outflows. You can also "net" multiple inflows (or outflows) into one transaction by just adding them all up, but typical business usage is to reduce the number of transactions by combining inflows and outflows.