Update README.md

Some details on the new ops.

initial-memcached/README.md

@@ -126,9 +126,9 @@ A little weirdly, `x` here is stored as a string, but converted to an integer to
 
 Now, we get to the feature set to add. It is small but to implement it you will have to understand the `memcached` code a bit. The features to add:
 
-- A `mult` command. This should look like `incr` and `decr` but do a multiply instead, e.g., if `x` was `10` to begin, `mult x 2` should result in `x` being set to `20`.
+- A `mult` command. This should look like `incr` and `decr` but do a multiply instead, e.g., if `x` was `10` to begin, `mult x 2` should result in `x` being set to `20` (this is standard C integer multiplication, which is implemented wit the `*` operator). The first argument should be an existing key, and the second argument an integer; anything else should fail in the same manner that `incr` fails. 
 
-- A `div` command. Same as above, but performing integer division, e.g., if `x` was `10` to begin, `div x 2` should result in `x` being set to `5`.
+- A `div` command. Same as above, but performing integer division, e.g., if `x` was `11` to begin, `div x 2` should result in `x` being set to `5` (this is standard C integer division, which is implemented with the `/` operator). The first argument should be an existing key, and the second argument an integer; anything else should fail in the same manner that `incr` fails. 
 
 That's it! 
 
@@ -142,3 +142,5 @@ Here are some tips:
 
 - *Determine what you can copy to make `mult` and `div` work*. Much of the code will be similar to `incr` and `decr`. What can you re-use to make it as easy as possible to realize the new features?
 
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