Oops, sorry

@@ -16 +16 @@
-<gloss g_type="lit">three-thousand ryō of white hair (nine kilometers)</gloss>
+<gloss g_type="lit">three-thousand jō of white hair (nine kilometers)</gloss>

originated from a work of Li Bai, a Tang dynasty poet

Sankoku tags [form]

1丈 = 3.03m
三千丈 = 3000 x 3.03 = 9090

9090m = 9km if rounded
Sankoku agrees: 三千丈＝約九キロメートル


Shinsen: しらがが長くのびていることを大げさに表現した言葉。
Oukoku also has "exaggeration" in its gloss

Adding xref to the unit 丈, compare e.g. the entry for 小便一町糞一里 (a fabulous proverb if you ask me)

.

"as an example of exaggeration for dramatic effect" sounds a bit odd to me. I think that note can be shortened

I think if a lit gloss is used the original unit's name should be used in it

Maybe like this?

@@ -12 +12,3 @@
-<s_inf>oft. used as an example of exaggeration for dramatic effect</s_inf>
+<xref type="see" seq="2145400">丈・じょう・1</xref>
+<misc>&form;</misc>
+<s_inf>oft. used hyperbolically</s_inf>
@@ -14 +16 @@
-<gloss g_type="lit">ninety kilometers of white hair</gloss>
+<gloss g_type="lit">three-thousand ryō of white hair (nine kilometers)</gloss>

https://x.com/ShinAmamiya0907/status/1926763877842235517
https://x.com/JoeKoizumiBot/status/1906311667685990564

Looking at some twitter usage, it looks like this is used to express something that's way over the top or exaggerated. Maybe worth adding a note and a literal definition too like this?

Also, I think the length conversion is right.

@@ -11,0 +12 @@
+<s_inf>oft. used as an example of exaggeration for dramatic effect</s_inf>
@@ -12,0 +14 @@
+<gloss g_type="lit">ninety kilometers of white hair</gloss>

@@ -12 +12 @@
-<gloss>many years of stress and anxiety (causing one's hair to grow white)</gloss>
+<gloss>many years of stress and anxiety (as would cause one's hair to grow white)</gloss>