PostgreSQL Optimization – Managing Schema Size with PG TOAST

I've got the following query to measure the schema's size on my DB:

WITH schema_size AS (
SELECT
tab.table_catalog AS database_name,
tab.table_schema AS schema_name,
tab.table_name,
pg_total_relation_size(table_schema || '.' || tab.table_name) AS table_size_total,
pg_relation_size(table_schema || '.' || tab.table_name) AS table_size
FROM information_schema.tables tab
WHERE table_schema NOT IN ('pg_catalog', 'information_schema')
), pretty_size AS (
SELECT
database_name,
schema_name,
pg_database_size(database_name) AS database_size_bigint,
pg_size_pretty(pg_database_size(database_name)) AS database_size,
sum(table_size_total) AS schema_size_bigint_total,
pg_size_pretty(sum(table_size_total)) AS schema_size_total,
sum(table_size) AS schema_size_bigint,
pg_size_pretty(sum(table_size)) AS schema_size
FROM schema_size
GROUP BY database_name, schema_name
)
SELECT
database_name,
schema_name,
database_size,
schema_size_total,
schema_size,
((schema_size_bigint_total * 100) / database_size_bigint) AS perc_total,
((schema_size_bigint * 100) / database_size_bigint) AS perc
FROM pretty_size;

However, when running it I get this information:

My DB is 2 TB and that schema is 1.7 TB.

Question:

Is that related to the toast tables? How can I decrease the size of it?