ICU-20469 Updating how to control ucadata type in userguide.
diff --git a/docs/userguide/icu_data/buildtool.md b/docs/userguide/icu_data/buildtool.md
index cebde5e..839db06 100644
--- a/docs/userguide/icu_data/buildtool.md
+++ b/docs/userguide/icu_data/buildtool.md
@@ -606,14 +606,11 @@
By default, the unihan version is used. The unihan version of the data file
is much larger than that for implicithan, so if you need collation but also
small data, then you may want to select the implicithan version. To use the
-implicithan version, pass the following command line argument to buildtool:
+implicithan version, put the following setting in your *filters.json* file:
- --collation_ucadata=implicithan
-
-To pass this argument when using configure/make or Windows makedata.mak, set
-it in the `ICU_DATA_BUILDTOOL_OPTS` environment variable:
-
- ICU_DATA_BUILDTOOL_OPTS="--collation_ucadata=implicithan"
+ {
+ "collationUCAData": "implicithan"
+ }
### File Substitution
