That's standard Leibniz notation from Calculus.

The problem you are running into is that every book starting in the late 1970s has taken the approach that you must know math intuitively to first translate the subjects being taught and to understand the modeled behaviors they represent.

Intuitive approaches have largely been ignored and avoided since then, and its acted as a gatekeeper ever since to prevent people from going into Physics, Science, and the other more technical fields.

This behavior follows practices of ideology common to gnosticism, which as a TL;DR is the idea that some people are allowed access to secret knowledge and others aren't, and only such masters can tell and determine who should have and be able to learn that knowledge. It is a completely refuted false ideology when it comes to objective reality, has no basis, and is quite evil since in practice to do this you impose a complex system of torture to ensure anyone seeking this knowledge that is deemed unworthy by some arbitrary measure is conditioned towards PTSD, just like any dystopia. They are made to believe they just aren't good at math.

This was a purposeful choice made by the boomer generation of teachers in their professions, given the widespread adoption was systematic. They simply followed what they were taught by the NEA, and that is why things are falling apart today. Knowledge of critical education was withheld, options were withheld, and by constraining thought they enforce a path of control, and the dynamics which inevitably culminate in destruction or annihilation given sufficient time because they don't stop making these changes. It gets to a point where you have people who are no better than dependent parasites on the labor of few educated, but not necessarily intelligent people. Hubris naturally occurs in such people.

The limit is also a calculus item. There is a derivative which is the instantaneous rate of change at a point (the slope is the average rate of change between two points) the single point and limit technique is always with respect to some other measure, and a integral which is the area under a curve at a single point, as the change between the points goes to 0 (i.e. a limit).

You use the delta form of the limit to calculate derivatives before you learn and have proved the shorthand methods with delta epsilon rigor. Its quite abstract, and the vast majority of the material is useless to a non-math/Engineer major. You need to understand this before you can read this.

> Does this equation actually take the effect of this fluctuation

No, the equation shown is a theoretical model, in math. In many cases, you are taught lies initially because they are simple, and a pedagogical tool called lying to children has been used since the late 70s, in various forms though wasn't called that until the 90s. Then you have to unlearn those lies as you progress through gnosis.

The best way to learn these things that I've seen that is still in use today is called Lumped Matter Discipline. It makes certain assumptions about the type of components in use to simplify the equations to basic algebra. You still need to know Calculus enough to Derive Maxwells theorems when those assumptions don't hold. One of the assumptions made is that charge buildup is 0 (iirc), in other words the second derivative, or the derivative of dQ/dt is 0, which is the acceleration or rate of rate of change.

The MIT OCW videos cover these simplifications, its dry, but its better than 99% of the other material out there aside from maybe the Oliver Heaviside Lectures at the turn of the last century which are public domain.

The flowing water pipe analogy which brainwashed/indoctrinated people use to teach is intended to purposefully mislead, maybe not by the instructor, but by the person they took it from.

Understanding the process of diffusion of charge and the need for isolation is the correct way to be thinking of these things.