50 to 150 is a hella broad range for any addition to be considered a "recommendation", imo...
Can you reference the recommendation? I am assuming it also includes ranges for Mg, Na, Cl, S04 - which should help us understand the recommendation.
Almost all of the target water profiles I am aware of use a single value (rather than a range). The recommendation is typically based on beer style or beer color. Often there's additional information associated with each ion.
Experts often have different opinions (for example: is 50 ppm Ca enough for a good mash? or is 100ppm needed?) - so focusing on a specific target profile recommendation may yield a 'better' discussion.
I was just throwing a random number out for some sort of reference point. Nothing particular. I probably should have been more specific (sorry).
If it it helps though, how about these numbers (from Brewfather)..........
For a hoppy pale ale:
My source water profile:
Ca2- 11, Mg2- 2, Na- 3, Cl-4, SO4- 6, HCO3- 33
Target profile (Hoppy):
Ca2- 110, Mg2- 18, Na-16, Cl-50, SO4-275, HCO3- 33
in Brewfather right below the target profile box, you can select a style (optional), so choosing American Pale Ale shows min/max numbers as:
Ca2- 50-150, Mg2- 0-30, Na- 0-100, Cl-0-100, S04- 100-400, HC03- 40-120.
So, going by the above (and using the Ca numbers for reference), My water profile shows 11ppm of Calcium. Should I add enough calcium chloride to hit the 11 in the target profile, or do I shoot for the min 50, max 150, or the middle of the road point of a 100 in the American Pale Ale guideline?
I know each addition isn't going to be cut/dry because each mineral can be in at least two additions (ex Gypsum and Calcium Chloride both have calcium in it). Maybe I'm overthinking this and I apologize if I am. If the recipe is important to know, it's just a variation of Bell's Two Hearted with a lower gravity and Cascade hops vs Centennial.