Count buyer no of 1st channel & source within date range

[elaineng]

I have two tables:
1) Buyer (buyerid, name, age,...)

2) Buyer activity (buyer activityid, buyerid, date, channel, source, etc)

I need to create a table which count the buyer no for 1st channel and source within the buyer activity date range selected by user.

[elaineng]

I tried:
dimension: channel 
Exp: = count(IF(BuyerActivity_createdon = Aggr(Min(BuyerActivity_createdon), buyerid), buyerid))

It will give me the result I want

But if I selected date, it is not providing the correct result. Eg: 02/01/2023 7:12:33 PM onwards

Landing page should count as 1 as it is the earliest record.