Question to do backups every hour and it's safeness

I have a question about incremental backups. I’m using server version 2.4.12 and clients have versions between and I want to know if i set image backups every 0.0416667 days will the backups be created every hour. Is it maybe an option not to use decimal record and change days option into hours. If it’s not possible how secure it is to use decimal record? Could any future update break it?
Also what will happen if backup doesnt complete in 1 hour. Will the new pending backup request wait or it will it break the first one?

In pictures you can see what i’m talking about, but here i put backup every 2.4 hours.