It's because coin market cap was displaying the value in M-IOTA instead of IOTA but had labelled it IOTA, then they decided to display the value in IOTA, then they went back to M-IOTA labelled IOTA.
(1 M-IOTA is 1 000 000 IOTA) M is for Mega.
IOTA - The Cryptocurrency That Jumped Into 6th Position
It's because coin market cap was displaying the value in M-IOTA instead of IOTA but had labelled it IOTA, then they decided to display the value in IOTA, then they went back to M-IOTA labelled IOTA.
(1 M-IOTA is 1 000 000 IOTA) M is for Mega.