diff --git a/README.md b/README.md
index 72dbe8b..26631ec 100644
--- a/README.md
+++ b/README.md
@@ -7,7 +7,8 @@ Roadmap:
 1. Install over.ts and get an example of add with number and bigint implementations working with it.
 2. Use the builder pattern to get add working with its implmentations defined incrementally before producing the final overload.
 3. Use the builder pattern to get a single object with both an add and a negate method, with both defined incrementally, working.
-4. Incorporate a subtract method that works generically with both add and negate, with just one generic implementation.
+4. Incorporate a subtract method that works on numbers and bigint by separate definitions but with dependencies on add and negate.
+5. Incorporate a subtract method that works with one generic implementation that works for both number and bigint with dependencies on add and negate.
 5. Attempt to eliminate redundant specification of implementation signatures.
 6. Incorporate multi-argument reducing implementation of add.
 7. Actually split into multiple source files to make sure that works.