How to modify wal_keep_size

Hi,
I've set up a 3-node pg_autofailover cluster with 2 data nodes and one monitor to ensure database availability. The databases are small (~ 2GB total), but high availability is critical.
My concern is the pg_wal folder growing to around 8GB. I understand WAL retention, but for my use case, 2GB should be sufficient.
I tried modifying pgautofailover.conf, but it seems to be regenerated at each daemon start.
How can I adjust the WAL retention size?

Current configuration:

```
postgres=# select name, setting, unit from pg_settings where name ='wal_keep_size';
name | setting | unit
---------------+---------+------
wal_keep_size | 8192 | MB
(1 ligne)
```

Thank you for helping