I like it. Mark is assuming 6 seams per colony on average and 5 ml per seam, and that is a reasonable assumption.
i) be explicit that the target concentration is 4.5% (w/v) of oxalic acid dihydrate which some call 3.2% (w/v) oxalic acid anhydrous
ii) rather than say no. of 10 frame colonies, just say 'full-sized colonies' and maybe indicate somewhere that you are assuming a mean number of 6 seams of bees and 5ml per seam of bees.
iii) maybe you should acknowledge that although this concentration has been widely adopted, some beekeepers use a lower concentration of 3.5% (w/v) oxalic acid dihydrate. The reasons for this are discussed in:
The figure of 50ml per colony is the absolute maximum that could be used in a 10 frame hive.
In my case I made up 550ml using the well published 100gm,100ml.7.5gm recipe and applied 5ml per seam of bees to my 11 colonies, I had more than 100ml left over.
My method is to trickle the first (apparently) empty seam next to the cluster, then all the seams with bees , and finally the next (apparently) empty seam. Ergo, in my case average seams trickled 8 per colony, average seams of bee per colony 6.
Checking the varroa drop 3 days later showed a debris area under where the cluster is plus two lines of OA droplets either side so I reckon they all got the best treatment possible and none were missed.
Unless poly, or seriously insulated wood, there will be no bees anywhere near the outsides of end frames (unless getting short of stores) yet. There will only be nine spaces for ten frames, as well. This is bucket chemistry, not analytical!
If I could only weigh 30g with any accuracy, I would simply split the resultant pile into half, or even quarters. It needs to be no more accurate than best you can do by eye.
Or dissolve in water and use half that aqueous solution made (for 15g oxalic), and discard, or store, the remainder.
Look, they say 5ml per seam. A 'seam' in a Langstroth is going to be different than a 'seam' in a National. Clusters are different sizes. So many variables that an average is just that - close enough. There is obviously some lattitude on safe dose. In simple terms that will be more easily exceeded if the oxalic is already very much towards the higher end of the safe range. As Hivemaker has said, probably more risk to the colony if they are nosemic, as long as the guidelines are followed.