added some help about decoding complex data in WriteProperty example app. (#627)

apps/writepropm/main.c

@@ -198,11 +198,11 @@ static void print_help(char *filename)
         "Device Object 123, the device-instance would be 123.\n");
     printf("\n");
     printf("object-type:\n"
-        "The object type is object that you are reading. It\n"
+        "The object type is object that you are writing. It\n"
         "can be defined either as the object-type name string\n"
         "as defined in the BACnet specification, or as the\n"
         "integer value of the enumeration BACNET_OBJECT_TYPE\n"
-        "in bacenum.h. For example if you were reading Analog\n"
+        "in bacenum.h. For example if you were writing Analog\n"
         "Output 2, the object-type would be analog-output or 1.\n");
     printf("\n");
     printf("object-instance:\n"
@@ -235,6 +235,10 @@ static void print_help(char *filename)
         "use a tag of 4.\n"
         "Context tags are created using two tags in a row.  The context tag\n"
         "is preceded by a C.  Ctag tag. C2 4 creates a context 2 tagged REAL.\n");
+    printf(
+        "Complex data use the property argument and a tag number -1 to\n"
+        "lookup the appropriate internal application tag for the value.\n"
+        "The complex data value argument varies in its construction.\n");
     printf("\n");
     printf("value:\n"
         "The value is an ASCII representation of some type of data that you\n"