1.2 Note on early use of Scheduler

Author: Froussios

Part 1 - Getting Started/2. Key types.md

@@ -133,7 +133,9 @@ Late: 3
 Our late subscriber now missed the first value, which fell off the buffer of size 2. Similarily, old values fall off the buffer as time passes, when the subject is created with `createWithTime`
 
 ```java
-ReplaySubject<Integer> s = ReplaySubject.createWithTime(150, TimeUnit.MILLISECONDS, Schedulers.immediate());
+ReplaySubject<Integer> s = ReplaySubject.createWithTime(
+		150, TimeUnit.MILLISECONDS,
+		Schedulers.immediate());
 s.onNext(0);
 Thread.sleep(100);
 s.onNext(1);
@@ -150,6 +152,8 @@ Late: 2
 Late: 3
 ```
 
+Creating a `ReplaySubject` with time requires a `Scheduler`, which is Rx's way of keeping time. Feel free to ignore this for now, as we will properly introduce schedulers in the chapter about concurrency.
+
 `ReplaySubject.createWithTimeAndSize` limits both, which ever comes first.
 
 ### BehaviorSubject