There is no need to make a malto dilution in water. The reason we do that with Karo is because its VERY difficult to accurately measure out "goo". 50/50 Karo/vodka is nearly water thin and an eyedropper will very accurately meter it out.
The vodka is used as the alcohol in it prevents the stuff from evolving life which any sugar in water will do by itself over time. Vodka (80 proof) is 40% alcohol, the rest being water so a 50:50 dilution would contain 20% alcohol (40proof).
Some people make a solution of glucose but the reasoning for this is that you need so little of it, it can become problematic to weigh it out (example: 1l, 20PPM needs 16.17milligrams of the stuff - thats 0.01617 grams and this requires a VERY expensive lab grade balance to accomplish). The opposite is true for malto - you need a LOT.
Malto? Just weigh it out, dump it into the water and stir. It will dissolve VERY quickly.
For a list of useful formulas for reducing agents, gelatine,... look here (second post in the linked topic by cfnisbet):
https://www.cgcsforum.org/index.php?topic=47.0For 20PPM, 1 liter, you need a minimum of nearly 0.3 grams of malto. For 60PPM, 0.9 grams.
I always add 10-20% more for good measure. A bit more reducer will speed up the reduction process simply because of the proximity effect - more reducer means a greater concentration of reducer molecules around each produced, dissolved silver oxide molecule (hence a closer proximity) and the quicker one malto molecule can associate with one silver oxide molecule, the faster that molecule of silver oxide will be reduced.
Also, since malto works as a very good stabilizer (Karo is only good to about 20PPM unless you're gel-capping where the gelatine becomes a strong stabilizer), having more of it in solution helps stabilize the silver particles.
Silver is hydrophobic (it HATES water). It will be surrounded by the malto molecules which coat the silver particles, protecting each from sticking to other silver particles (agglomeration), hence keeping the silver particles as small as you made them initially, for the whole life of the Colloidal Silver suspension (a.k.a stabilizer).
An easier way would be to just figure out about what volume measure 300mg of malto is in powdered form (you can use more but not really any less - more won't hurt) and use one measure for 1 liter of 20PPM and 3 measures for 60PPM,... or just weigh it (wink).
In the grand scheme of things, weighing it takes maybe 1 minute tops and you only have to do that one time for each run where 1 run will take far longer than this.
Your choice.