battery charging

Perhaps this indicates you're the wrong guy to work on this project?

Maybe you should be chatting with the guys at Gaston, rather than those a Keil?

Perhaps this indicates you're the wrong guy to work on this project

BOOM

batteries tend to explode if the charger is made by "the wrong guy"

Not sure why you want me to study that document - you want me to write a battery charger for you?

An as you can see, the document does not write C8 - which for normal formulas would be expected to mean the same as C*8 and so be a meaningless figure since it's irrelevant do discuss "eight times the capacity of the battery". The text does write on quite a number of places C₈ - so the digit 8 is a clarification of exactly which capacity they mean. In this case the capacity the battery can supply for an 8-hour discharge speed. I saw one place where they missed to subscript but it was very clear this was a typographical mishap.

From what it looks like, the full sentence (that you should have supplied verbatim) that your first post seems to refer to is:
"The recommended recharge method of GT-F batteries to maximize battery life is to
use a constant voltage equal to the float charge voltage (2.27 VPC at 20°C) with a
maximum charge current of 0.25 C₈ amperes."

So you get a clear indication what C means. And then it's business as usual with the meaning of 0.25 C as maximum charge current. If C₈ is 100 Ah, then you must never get above the current that would charge the battery in four hours, i.e. 100 [Ah]*0.25[1/h] = 25 A (Alternatively expressed as 100Ah/4h = 25A) as charge current (to avoid cooking the battery cells). Since we are talking about constant voltage charging, we are talking about the charger using a current limiter for a while at the start of the charge cycle. The battery cells will later reach a state where the cells themselves decides how much current to accept based on the fixed charging voltage of 2.27 V/cell.

A problem when asking questions, is that the questions must contain enough context. Missing, important, context makes them meaningless. Supplying incorrect information is even worse when expecting a good answer. That's why links, paragraph numbers etc are so valuable when asking questions, allowing people reading the question to pick up additional context if needed.

The datasheet in question is for quite large batteries. Large batteries also means large accidents when things go wrong. Which means this isn't the kind of batteries to play with for people who need to ask basic questions about the meaning of the individual formulas. For these battery sizes, ventilation is also important unless you want the neighbors to inform you that your roof has left the building.