approximateCount confused

atlas should return search result total exactly when user post some search Conditions, like query string and filter.  Is using approximateCount as total?  but approximateCount make me confused.

a general scene： i want the total of search result for page i one request. but now i should recall api to add limit (eg: 100000+) .

the bad way: to reduce paramaters for get all and return hurge data for calculate.

Problem 1:

the response of post "/search/basic" api.

see picture1 ,  i'm not add filter and set search text to find the hive_table contains my custom attributes, the approximateCount is correct。 by the way, is DSL support find __customAttribute?? how to do?

picture 1:

see picture2,  i'm add filter and not set search text, the approximateCount is incorrect。 i see the correct total is 11 one by one.

picture2

also i can't using the entities size for work when the limit paramters changed. 

so how to search use defined attribute for work? use filter or fullText search? and is a bug? or need some total variable？ 

Problem 2:

Use-defined propertiies can help business . can support dsl search it ? any discuss will help me.