OK. So ルミナス和英辞典 has gone too far here.

i'm not comfortable with this merge.  the english translations are similar but 最小 and 最少 are quite different as they indicate size vs. quantity respectively.  the antonyms make that clear. 最小<-->最大 whereas 最少<-->最多.  it's similar to the difference between "less" and "fewer" in english

@@ -15,0 +15,1 @@
+<pos>&adj-no;</pos>
@@ -16,1 +17,5 @@
-<gloss>smallest</gloss>
+<xref type="ant" seq="1657750">最多</xref>
+<gloss>fewest</gloss>
+<gloss>least</gloss>
+<gloss>smallest (number)</gloss>
+<gloss>lowest</gloss>
@@ -18,1 +23,6 @@
-<gloss>least</gloss>
+</sense>
+<sense>
+<pos>&adj-no;</pos>
+<pos>&n;</pos>
+<xref type="ant" seq="1657760">最長・2</xref>
+<gloss>youngest</gloss>

I see ルミナス merges 最小 and 最少, so I'm going to propose that here.

See below.

I have tended to regard the above in terms of quantity and the following in terms of size.

最小 【さいしょう】 (n,adj-no) smallest; least; (P)

It is clear from Google images that there is a significant overlap in usage and I am wondering if you would consider a cross-reference between the two entries. Should you also think on the same lines about quantity and size in the sense that there are some definite occasions when one must use one or the other, then perhaps that distinction can be incorporated without eliminating the common factor.

I have not made an input into the actual text because I guess that I would tend to go overboard with my descriptive tendency.