His 663,000 total includes those being detained.
Note also, these appear to be criminal records from their former countries. We don't know the context.
What this tells us is a couple things we already knew. ICE doesn't have sufficient detention facilities, and the immigration courts don't have enough Judges, etc..
A sizable part of the problem is due to Trump's zero tolerance policy of prosecuting simple unlawful entry as a crime. That made them eligible for trials, attorneys, etc.
Technically, simple unlawful entry has been a crime since 1929. However, it was previously treated like unlawful presence, as a civil offense, handled by administrative processes -- unless there were aggravating factors such as additional crimes.
Trump's policy created a back log, and diverted resources from actual serious criminals.