Why are dynamic rules not created in Mangle?

Question

Mikrotik

The situation is this:
There is a router with a white IP, it goes to the Internet via PPTP, in the properties of PPP - Profiles there is a check mark on - Change TCP MSS.
I remember that a year ago, 2 rules were created in Mangle - Change MSS, for incoming and outgoing and outgoing PPP interfaces.
Today I have to manually create a rule in the mangle, but there is a problem with the correct choice of TCP MSS - there are suspicions that I have not quite the right values.
Today I went to another office, and noticed that there are those rules in the mangles that were created automatically - and it seems like they say - take it according to the template - but they have different connection types and different MTUs

Answer 1

Release 6.39 2017-04-28
What's new in 6.39 (2017-Apr-27 10:06):
...
!) ppp - implemented internal algorithm for "change-mss", no mangle rules necessary;
...
If dynamic rules are created in the mangle table, update the version of Router OS.