In – After "in” we always have a period of time

"In” tells us really well when something will happen in the future

"In 10 minutes" means 10 minutes from now.

If I am in the kitchen with you, teaching you how to bake a cake, we might have just put the cake into the oven, and then I might tell you "Take it out in 10 minutes".

After – Usually refers to a moment. It can be used with expressions about the past or the future.

"He will come after the meeting” or "He came after the meeting.”

The meeting starts at 7.30 a.m.
The meeting ends in 30 minutes. It ends at 8.00 a.m.
(Meeting doesn't go on more than 30 minutes. There won't be a meeting at 8.01 a.m.)

You can leave after 30 minutes.
(You may or may not leave at 8.00 a.m. You may leave at 8.30 a.m. too.)

The end of the meeting is in 30 minutes so you may leave after the end of the meeting (a moment).

When we use "after” with period of time we are referring to the moment which comes immediately after that period of time.

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