CoachA position in an instrument is the signed quantity held: positive (long) if owned, negative (short) if owed. It changes only through fills, corporate actions and transfers; it is the sum of the signed quantities of all of them since inception.
Exemples
Example 7.3 (A long–short book)
Long $300 million and short $200 million on $100 million of equity: gross $500 million, or the equity, the measure of how much can go wrong; net $100 million, or , the measure of how much market direction is being taken. Limits are set on both, and on each position separately.