The CBT is two exams in one appointment
Most people book the CBT thinking of it as one exam. It is easier to prepare for once you see it as two, sat back to back, marked separately.
You sit down once and you are there for three hours. In that time you answer one hundred and fifteen questions. The first fifteen are numeracy and you get thirty minutes for them. The remaining hundred are clinical and you get two and a half hours. The two parts have their own clocks, and running out of time on one does not borrow from the other. More importantly, they have their own results. You can pass one and fail the other, and that is a common outcome rather than an unusual one.
The numeracy part works differently from anything else in the exam. There are no options to choose from. You work the answer out and you type it in, with a calculator on the screen and an erasable note board on the desk, though you are not allowed to write on the board until the tutorial has finished. Getting the arithmetic right is only half of it. You have to give the answer in the form the question asked for, which means reading the lead in properly and noticing whether it wants millilitres or milligrams, and whether it wants a whole number.
The clinical part is four options with one best answer, and it is built on the NMC's blueprint rather than on general nursing knowledge. The questions come from the seven Future Nurse platforms plus the two annexes, and the NMC publishes how many questions come from each area. Around nine tenths of the content is common to all four fields of practice, and about a tenth of the clinical part is specific to the field you registered under.
One mark per question throughout, no partial credit, and nothing taken off for a wrong answer. That last point is worth acting on. There is no reason to leave anything blank. If you are down to two options and the clock is going, pick one and move on.
The practical consequence of all this is that practising a mixed set of questions for an hour is not the same as preparing for the exam. Numeracy under thirty minutes of pressure is a different skill from clinical reasoning under two and a half hours, and most people are noticeably weaker at one of them. Sitting them the way the exam does it, in two separately timed parts in one go, is how you find out which one that is while it still costs you nothing.
Our mocks are built that way for exactly that reason. Both parts are generated together, both run on their own clock, and each is submitted and marked on its own, so what comes back tells you the same thing your result letter will.