If you were not expecting it, a number already sitting in the quantity box looks like a fault. It is not, and the way it is scoped is more careful than it first appears.
Each instrument remembers separately
The memory is per instrument, not per account. Your gold size, your EUR/USD size and your BTC size are stored independently and never bleed into one another.
This matters because size means different things in different markets. A sensible quantity on a major forex pair is a very different number from a sensible quantity on a volatile token, and a single remembered value carried across both would be worse than no memory at all.
An instrument you have never traded starts at zero. Nothing is guessed, extrapolated, or borrowed from a similar market.
The feature works across perpetuals, forex and LOT-based instruments on derivatives.
Why it exists
Most traders repeat the same size on the same markets. If you always trade 0.5 lots of gold, typing 0.5 every time is a small tax on every trade, and small taxes on repeated actions are where mistyped sizes come from.
The memory removes the retyping. That is the whole feature, and it is worth exactly what it sounds like it is worth.
The habit worth keeping
A pre-filled field is a convenience, not a decision. The right size for a trade depends on the setup, on how far away your stop sits, and on what else is open in the account, none of which the platform knows when it fills the box in.
So the same check applies as always: before confirming, look at the quantity and look at the estimated liquidation price beneath it. If the remembered size was set when your account balance was different, or when you had no other positions open, it may no longer be the size you want. The figure that tells you is already on the screen.
That is not a warning about this feature specifically. It is the same check that should follow any quantity, typed or remembered.
FAQ
Why is a quantity already filled in when I open an instrument? Ouinex remembers the last quantity you traded on that specific instrument and pre-fills it. It is a convenience feature, not a recommendation, and you can overwrite it before placing the order.
Does the remembered quantity carry across different instruments? No. Each instrument keeps its own separate memory, so your forex size, commodity size and crypto size are stored independently. An instrument you have never traded starts at zero.
Can I turn off the quantity memory? The field is always editable, clear it or type over it before confirming, and the new value becomes the remembered one for that instrument.
Which markets does it apply to? Perpetuals, forex and LOT-based instruments on derivatives.
The bottom line
A number in the quantity box means you have traded this instrument before at that size. Check it against your current account and your stop distance rather than accepting it by reflex, and overwrite it whenever the trade calls for something different. More on the 4.35 release is in the full changelog.