Lot

A bundling convention, not a quantity in its own right. In foreign exchange one convention covers the class: a standard lot is a fixed number of units of the base currency, with mini and micro lots defined as stated fractions of it. Elsewhere the unit is physical or contractual and there is no single convention at all, so a lot is a stated quantity of ounces, of barrels, of shares, or an amount of money per index point, published instrument by instrument in the contract specification.

Everything downstream is built from it. Notional value is the number of lots multiplied by the contract size and then by the price. The value of a pip or a tick is the contract size multiplied by the size of that increment, scaled by the number of lots. The smallest volume that can be dealt and the step between one volume and the next are set per instrument by the firm, so an order rounds to that step rather than to any round number a reader has in mind.

The trip is treating the word as a unit of size that travels between markets. It does not: the same stated volume in two instruments is two different exposures, sometimes by a wide margin, and the figure is meaningless until the specification has been read. A second and quieter error is treating volume as a measure of risk. What is at stake on a position follows from the volume, the contract size and the distance between the entry and the exit, and volume alone reports only the first of those three.