Select Rows within a Group based on a condition

Question

 CREATE TEMPORARY TABLE TempSlotUpdated (
  slotId         INT(10)   NULL,
  slotstarttime  datetime  NULL,
  slotendtime    datetime  NULL,
  totalTime      time      NULL);


CREATE TABLE `Apt` (
  `slot_Id`           int(10) unsigned DEFAULT NULL,
  `apt_Id`            int(10) unsigned DEFAULT NULL,
  `time`              time NOT NULL,
  `assigned_To_Id`    int(10) unsigned NOT NULL,
  `created_At`        datetime NOT NULL DEFAULT CURRENT_TIMESTAMP,

) ENGINE=InnoDB DEFAULT CHARSET=latin1

Now, lets say if the Slots are updated so I need to delete some appointments e.g.

Apt Table :

| slot_Id | apt_Id | time     | assigned_To_Id | created_At
| 2634    | 129    | 00:25:00 | 2              | 2018-10-25 16:00:00
| 2634    | 132    | 00:30:00 | 2              | 2018-10-26 16:40:00 
| 2635    | 156    | 00:20:00 | 2              | 2018-10-27 16:00:00
| 2635    | 160    | 00:25:00 | 2              | 2018-10-27 16:40:00

TempSlotUpdated Table has :

| slotId | slotstarttime          | slotendtime         | totalTime 
| 2634   | 2018-10-31 16:00:00    | 2018-10-31 16:30:00 |  00:30:00 
| 2635   | 2018-10-30 16:00:00    | 2018-10-30 16:30:00 |  00:30:00 

Now, the slotId 2634 which initially lets say had 1 hour totalTime now only has 30 mins totalTime, so I need to find out the latest appointments that have to be reassigned/deleted.

So referring to Apt Table,

it will be record with apt_Id = 132 for slot_Id = 2634
&          record with apt_Id = 160 for slot_Id = 2635

I tried using Group By and Having but I am not sure how to use a condition for set of rows inside a Group.

This is what I Tried :

SET @suma = TIME('00:00:00');

Select * from
         (SELECT @suma:= ADDTIME(@suma, `time`) , CAST(@suma as Time) 
          as time2, apt_Id 
          FROM Apt 
          WHERE slot_Id = 2634
          ORDER BY Apt.created_At ASC) 
          as abc
          Where abc.time2 >= TIME('00:30:00');

I tried with hard coded value and this works for one value of slot ie. 2634 and 00:30:00 totalTime I am now trying to use it with TempSlotUpdated table now which has multiple slots whose totalTime has changed.