Concurrent Users in the database investigation

Has anyone compared two datetimes to see if they are in the same time frame?

Our contract with hosting services allows us 10 concurrent users.

Nobody users were complaining, but I had a hunch we might be close to that limit.

I wrote some SQL to find count the max users per day aggregated per day over the last 6 months:

from the table TA_AUDIT_LOGON_INTERNAL, which i'm hoping was the right table for a login history table. 

the table looks like this: 

SQL:

SELECT
    CAST(logon_dt AS DATE) AS ActivityDate,
    COUNT(DISTINCT user_id) AS UniqueUserCount
FROM
    TA_AUDIT_LOGON_INTERNAL
WHERE
    logon_dt >= DATEADD(MONTH, -6, GETDATE())
    AND status = 0
GROUP BY
    CAST(logon_dt AS DATE)
ORDER BY
    ActivityDate;

/*
TA_AUDIT_LOGIN_INTERNAL status dictionary

0 = successful login

1 = invalid tessitura login

2 = login is already locked

3 = SQL Server login failed

4 = too many invalid attempts so locking login

5 = invalid password entered

6 = no app access per group security settings

*/

result:

graphed it out in excel: 

so i can see we have max 20 users per day, but on average12ish per day. So we need probably need to increase our concurrent user limit. 

This was a great, but i'm curious to actually count concurrent users (not just total users) by comparing logon_dt to logout_dt aggregated per day?

I'm thinking of a third column and the logic would be something like "If count of concurrent users >10 then "1" and then have some subquery to compare time frames per day and count how many"

just confused on how to do that!

Any help is appreciated!