Update oplog-replay.md (#323)

Update doplog-replay.md

Added info about using (epoch, ordinal) pair

Author: igroene

docs/usage/oplog-replay.md

@@ -13,26 +13,47 @@ By replaying these oplog slices on top of the backup snapshot with the [`pbm opl
 
     Use the oplog replay functionality with caution, only when you are sure about the starting time from which to replay oplog. The oplog replay does not guarantee data consistency when restoring from any backup. However, it is less error-prone for backups made with Percona Backup for MongoDB.
 
+## Ways to specify time for oplog replay
+
+PBM uses MongoDB's timestamp format for oplog replay, which provides operation-level resolution. Each oplog operation is identified by `(epoch, ordinal)`, where `epoch` is the Unix time in seconds and `ordinal` distinguishes multiple operations within the same second. The specified operation is always included in the replay.
+
+You can define the oplog replay stop point in two ways:
+
+1. **By ISO timestamp**:  
+   Specify an end time as an ISO timestamp (for example, `2025-01-02T15:00:00`). Use this method when you want to include all operations that occurred until the specified second.
+
+2. **By MongoDB timestamp tuple**:  
+   Specify the stop point as `epoch,ordinal` (e.g., `1764576382,20`). PBM includes all operations up to that exact operation. Use this method when you need precise control over which specific operations within a second to include. 
+
 ## Oplog replay for physical backups
 
 !!! note ""
 
     Starting with version 2.2.0, oplog replay on top of a physical backups made with Percona Backup for MongoDB is done automatically as part of [point-in-time recovery](pitr-physical.md). 
 
-This section describes how to manually replay oplog on top of physical backups with Percona Backup for MongoDB version 2.1.0 and earlier.
+This section describes how to **manually** replay oplog on top of physical backups made with Percona Backup for MongoDB version 2.1.0 and earlier.
 
 After you [restored a physical backup](restore.md), do the following:
 
 1. Stop point-in-time recovery, if enabled, to release the lock.
 
 2. Run `pbm status` or `pbm list` commands to find oplog chunks available for replay.
 
+3. Run the `pbm oplog-replay` command and specify the `--start` and `--end` flags. See [how you can specify the time](#ways-to-specify-time-for-oplog-replay).
 
-3. Run the `pbm oplog-replay` command and specify the `--start` and `--end` flags with the timestamps.
+    === "Use timestamp"
 
-    ```bash
-    pbm oplog-replay --start="2022-01-02T15:00:00" --end="2022-01-03T15:00:00"
-    ```
+        ```bash
+        pbm oplog-replay --start="{{year}}-01-02T15:00:00" --end="{{year}}-01-03T15:00:00"
+        ```
+    
+    === "Use `epoch,ordinal`"
+
+        For a fine-grained precision which exactly operations within a second to include, specify the values for the `--start` and `--end` flags as `epoch,ordinal` tuples.
+
+        ```bash
+        pbm oplog-replay --end “1764576382,100”
+        ``` 
 
 4. After the oplog replay, make a fresh backup and enable the point-in-time recovery oplog slicing.