Analysis of information sources in references of the Wikipedia article "2020 Democratic Party presidential primaries" in English language version.
A few states use divisions other than congressional districts. For example, Texas uses state senatorial districts. However, the broad point is the same – there are separate statewide and 'local' proportional delegate allocations.
The AP delegate estimate reached the magic number of 1,991 delegates for Biden as seven states and the District of Columbia continue counting votes from Tuesday's primaries
That gave Biden five of Guam's seven pledged delegates, pushing him over the 1,991-delegate threshold to clinch the nomination