It's really a challenge, to attempt as close to an integer decrement as possible. Certainly, with the multiplier in this suggested style of analog 'stamps', with the multiplier being digital as a discrete integer, I.E. whole, discreet quantities of the Multiplicand are transfered.

Then, you have the multiplicand, a wide open analog quantity. Exploration of substituting the modifying function that IS possible, (vs. integer decrement), one choice could be:

Multiply by 8/10: The downward steps would be:

{ 9, 7.2, 5.76, 4.608...} which could be considered as too little, compared with goal, to closely look like an integer decrement; { 9, 8, 7, 6, etc.}.

Using multiply by 9/10 each, the sequence w/be:

{ 9, 8.1, 7.29, 6.561, 5.90} which you can see, gets down to '5.9' whereas a straight integer decrement would get you down to 5.0 (integer). So, that choice of

÷10 and X9 could be deemed as 'too much', while the former choice of ÷10 and X8 could be deemed as 'too little' of an approximation, of integer count-down.

All this is fascinating and confusing territory, and at the same time !

In order to do a finer multiply, could next try X.85, remembering it's DISCRETE, not analog. So, you need a scale using 2 decimal digits. That would be an apparatus having 100 'flaps', closing 15 of them to get that 0.85 ratio.

I'll have to work out those numbers, but point is, trying to get best closest match, as substitute function for the discrete subtraction, of each 'i' step in a FOR-NEXT

structure (unwound loop). You still won't be able to use that 'step' parameter directly in integer form, such as to read 'memory' at $4010 + 'i' offset. Discrete means all or nothing, of the multiplicand copies stamped out.

Of course, any 'copy' of the light beam amplitude is made by splitting the beam, proportionally, and downgrading the 'value' scale. So, for example, having a beam at 100 lumens, split in two, the 'new' standard full signal would be downgraded to 50 lumens, that being the case for either new 'sub-beam' , as they proceed on their way, into next appropriate passive logic section.