diff --git a/docs/source_docs/inputs/InputsCheckpoint.rst b/docs/source_docs/inputs/InputsCheckpoint.rst
index 777b61a7399a491467e467cbe78877af5165df65..33ce629d4a71f24f46e7d96b6a6e5bd998f8c013 100644
--- a/docs/source_docs/inputs/InputsCheckpoint.rst
+++ b/docs/source_docs/inputs/InputsCheckpoint.rst
@@ -10,14 +10,21 @@ The following inputs must be preceded by "mfix." and control checkpoint/restart.
 +=========================+=======================================================================+=============+===========+
 | restart                 | If present, then the name of file to restart from                     |    String   | None      |
 +-------------------------+-----------------------------------------------------------------------+-------------+-----------+
-| check_int               | Frequency of checkpoint output;                                       |    Int      | -1        |
+| check_int               | Frequency of checkpoint output in timesteps number;                   |    Int      | -1        |
 |                         | if -1 then no checkpoints will be written                             |             |           |
 +-------------------------+-----------------------------------------------------------------------+-------------+-----------+
+| check_per_approx        | Frequency of checkpoint output in simulation time;                    |    Real     | 0         |
+|                         | if 0 then no checkpoints will be written                              |             |           |
++-------------------------+-----------------------------------------------------------------------+-------------+-----------+
 | check_file              | Prefix to use for checkpoint output                                   |  String     | chk       |
 +-------------------------+-----------------------------------------------------------------------+-------------+-----------+
-| check_walltime          | Write a check point file after the specified walltime (HH:MM:SS)      |  String     | None      |
-|                         | has lapsed. For example, if mfix.check_walltime = 00:10:00, then a    |             |           |
-|                         | checkpoint file is after a job has run for ten minutes.               |             |           |
+| check_walltime_limit    | Write a check point file before the specified walltime (HH:MM:SS)     |    Real     | -1        |
+|                         | has been reached. For example, if mfix.check_walltime_limit = 0:10:00 |             |           |
+|                         | then a checkpoint file is written a little time before the job has    |             |           |
+|                         | reached 10 minutes of runtime                                         |             |           |
++-------------------------+-----------------------------------------------------------------------+-------------+-----------+
+| check_walltime_buffer   | This is time subtracted to check_walltime_limit to avoid the job is   |    Real     | 300       |
+|                         | killed before mfix has completed writing the checkpoint file          |             |           |
 +-------------------------+-----------------------------------------------------------------------+-------------+-----------+
 | geom_chk_write          | When True, writes the EB geometry data into geom_chk_file             |  bool       | False     |
 |                         | and additionally, geom_refined_chk_file, if levelset                  |             |           |