[gnumeric] TRUNC: further doc fixes.

[Morten Welinder <mortenw src gnome org>]

commit b131f562de12d98fa902b0252d24a3f5c5697a7f
Author: Morten Welinder <terra gnome org>
Date:   Mon Aug 29 17:38:16 2022 -0400

    TRUNC: further doc fixes.

 plugins/fn-math/functions.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/plugins/fn-math/functions.c b/plugins/fn-math/functions.c
index 562d17d0b..e06e29586 100644
--- a/plugins/fn-math/functions.c
+++ b/plugins/fn-math/functions.c
@@ -1987,11 +1987,13 @@ gnumeric_pi (GnmFuncEvalInfo *ei, GnmValue const * const *argv)
 static GnmFuncHelp const help_trunc[] = {
        { GNM_FUNC_HELP_NAME, F_("TRUNC:@{x} truncated to @{d} digits")},
        { GNM_FUNC_HELP_ARG, F_("x:number")},
-       { GNM_FUNC_HELP_ARG, F_("d:non-negative integer, defaults to 0")},
+       { GNM_FUNC_HELP_ARG, F_("d:integer, defaults to 0")},
        { GNM_FUNC_HELP_NOTE, F_("If @{d} is omitted then it defaults to zero. If it is not an integer then 
it is truncated to an integer.")},
+       { GNM_FUNC_HELP_NOTE, F_("If @{d} is negative, it refers to number of digits before the decimal 
point.")},
        { GNM_FUNC_HELP_EXCEL, F_("This function is Excel compatible.") },
        { GNM_FUNC_HELP_EXAMPLES, "=TRUNC(35.12)"},
        { GNM_FUNC_HELP_EXAMPLES, "=TRUNC(43.15,1)"},
+       { GNM_FUNC_HELP_EXAMPLES, "=TRUNC(43.15,-1)"},
        { GNM_FUNC_HELP_SEEALSO, "INT"},
        { GNM_FUNC_HELP_END}
 };