Not best with formulas to be honest but...
https://youtu.be/URq1K46s3gw Before-616 After charm Activated- 1487. = 2.41396104 ( speed affected by depth Calcei -5) which gives basic 621 and 2,394524
@ 1.02 time it shows 621+ 866 which is the key for calculation of the charm effect. 866 is 1.3945... of 621- but does it mean it ignores -5 from Depth Calcei? Would that mean it also ignores any speed eq?
So the formula would be
X=base speed
x + 1.4x= Speed after charm is activated. BUT:
Considering forum examples -
https://www.tibia.com/forum/?action=thread&threadid=4649067
It means it Is multiplied by 2.354 of the base speed 410 with level 302, where it is 2.37 for Yiotoo with base 462 and level 353.
He mention that level is included in the formula- but I would not say it has crucial meaning in whole thing.
https://youtu.be/Nhoym1CGeKM Before-988 after charm activated - 2395 = 24208907 (unknown eq etc)
Unfortunately I don’t have this charm unlocked...