Considering the cost of your kits and the length of time invested, If you have some pH test tape you might want to check the pH.
This is a major factor in how much sulfiting is needed. Most wines finish at about pH 3 to pH 4 ... but there can be quite a bit of difference in the free sulfites needed between those numbers.
Without the sulfite testing (which often has it's own problems with accuracy and variability, I digress) adjusting sulfite additions up or down becomes a bit more an art than a science and a bit of a guess.
Furthermore, other factors go into the judgement such as exposure to microbes/pathogens/bacteria during your vinting process ... how oxygenated the wine has become from processes and handling ... and whites and lower tannin wines need a bit more than reds and higher tannin wines.
Briefly ... about pH and sulfites ...
The amount of molecular ("available") sulfite will depend on both the free, unbound sulfite (one number) in the wine; and the pH (another number).
In general terms, the higher the pH the (somewhat) heavier your sulfite requirement is.
How heavy??
At about pH 3.4 the free SO2 requirements start taking off (go up precipitously) to obtain a desired molecular SO2 level.
Not to glaze you over here, but for what it's worth ...
The real numbers for the increase in sulfites vs pH are not at all even and logarithmic. The sulfite requirements go up steeply the higher the pH.
For example (these numbers are approximate)...
To get a desirable 0.8mg/L molecular SO2 protection level ... at pH 3.4 it takes about 35mg/L of free sulfites (aka, ppm) ...
at pH 3.6 it takes about 42mg, so a difference of about 7mg for that extra two tenths of a pH point.
going up to pH 3.8 it is about 76 mg ... a difference of about 34mg for those next two tenths of a pH point (3.6 to 3.8)
... and for another two tenths of a point going from pH 3.8 up to pH 4.0; the free SO2 needed might be around 125mg - or an extra 50mg for that two tenths.
... like I say, it goes up fast ... for each additional two tenths in pH ... 7mg extra ... then 34mg extra ... then 50mg extra. Each for only a two tenths pH increase.
What does this mean? ...
While without testing you won't quite know where your molecular SO2 is at any time ... back-of-the-napkin I'd say for your red wine, at 3.6 the package instructions are ok ... but at 3.7 I'd say at the very minimum about 10% more ... and for 3.8 and 20% more.
These percentages are the amount of extra campden/metabisulfite ... noting that the amount of metabisulfite does not evenly equal the same increase in free sulfite in the solution ... so this is a very approximate recommendation. And very possibly a bit short.
Also note that commercial wines often have quite a bit more sulfite than used by home vintners. They have a lot to lose if a batch goes south. Commercial ranges go from about 10 to 40 for "no sulfite" wines - this is natural sulfiting from the fermentation process ... up to 350 ppm (350mg/Litre) in certain sweet whites. Yep, a broad range ... and a lot of latitude.
You can poke around with the following calculator if you like ...
https://winemakermag.com/1301-sulfite-calculator
Or, you could just bump it up a bit if by chance you are above pH 3.6 in a red ... or 3.4 in a white. Like I noted, there is a lot of leeway to the levels used in commercial wine production. For the sake of our pocketbooks, for wines subject to home winemaking practices that are going to be held for a while, increasing metabisulfite additions can be cheap insurance.
