a similar, but not exactly this problem occured for me too...
I was in a normal zone with a team member, then starting my opened challenge (before some minutes ago) & it looks like the pic in the attached screenshot. it never happened to me before, so it was the first time, when it happened to me so far, so I still thought, letting you know about it :-)
each challenge-enemy kill counted to the "kills" which are shown in the attachment. but after failing the challenge (because the enemy was still too strong), I had 29 / 45 kills at the epsilon-planet (zone 7 or 8 i think)
also the card-amount is shown in the e.g. mother's day event, but also in the normal event, like in the screenshot below.
I was in a normal zone with a team member, then starting my opened challenge (before some minutes ago) & it looks like the pic in the attached screenshot. it never happened to me before, so it was the first time, when it happened to me so far, so I still thought, letting you know about it :-)
each challenge-enemy kill counted to the "kills" which are shown in the attachment. but after failing the challenge (because the enemy was still too strong), I had 29 / 45 kills at the epsilon-planet (zone 7 or 8 i think)
also the card-amount is shown in the e.g. mother's day event, but also in the normal event, like in the screenshot below.