Measure time in ONLY HOUR format

I need to change the timeformat in this column (https://share.getcloudapp.com/bLuw6045) to be in hours, not measured in seconds and minutes. This meaning that 30 minutes should be measured in 0.5 hours and so on.

I think I need to edit this line of code. Any suggestions on how to change the measurement to ONLY HOURS?

return human_time_diff(strtotime($item[‘time_login’]), strtotime($item[‘time_last_seen’]));