So in short, what it is:
>Murderers, rapists, drug dealers, young-middle aged criminals, criminals who still have a significant sentence remaining
Pretty much stuck
>Criminals over 60, small offenders, people who maybe have just a few months left anyway
Good chance to leave early through a process.

What it isn't:

It's not that simple:
"Inmates with two months or less still to serve will be released on temporary licence in stages."
Source: https://www.bbc.com/news/uk-52165919

""A total of 22,158 inmates in Indonesia have been released in a bid to reduce the risk of coronavirus transmission in overcrowded detention facilities, an official said on Friday.

She said the released prisoners are those who have served two-thirds of their sentences.

However, the number does not include those convicted for corruption, terrorism, and drug-related crimes."
Source: https://www.aa.com.tr/en/asia-pacific/indonesia-releases-22-000-prisoners-over-covid-19-fears/1791209

"Authorities should examine ways to release those particularly vulnerable to COVID-19, among them older detainees and those who are sick, as well as low-risk offenders."
Source: https://www.france24.com/en/20200325-un-urges-prisoner-releases-to-stem-spread-of-coronavirus