With the Low Voltage Cell plate configuration the total current is shared by all the commonly connected plates. When the plates are interleaved, those plates which are between plates of the opposite polarity will be conducting on both sides to the opposite plates.
Therefore: Your plate size of 2.5" X 12" yields 30 square inches per side.
Assuming you have a total of 12 plates; 6 Anodes and 6 Cathodes interleaved, spaced at 1/8 inch; the total current your cell would be able to support at the 1/4 Ampere per square inch maximum is 82.5 Amperes.
Your total conductive surface area for the Anode group is 330 square inches.
Your total conductive surface area for the Cathode group is 330 square inches.
330 square inches X 0.25 Amperes = 82.5 Amperes.
That is the advantage of the low voltage cell. You take into account the total surface area of the conductive sides of your common plates.
I tried to explain the calculation process in the earlier post with an example of one plate and did not sufficiently clarify the procedure to find the total surface area of all the common plates; which is additive.