I have got a query:

explain analyze select tfield from tws order by tfield;

Query Plan is:

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Sort (cost=177824.04..181821.54 rows=159900 width=12) (actual
time=1991.637..2087.435 rows=159900 loops=1)
Sort Key: tfield
-> Seq Scan on tws (cost=0.00..39615.99 rows=159900 width=12) (actual
time=0.016..88.862 rows=159900 loops=1)
Total runtime: 2160.171 ms

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My question is "What is PostgreSQL doing between 88.862 and 1991.637
milisecond?"