Getting a cross mark on an assessment basically means "poor". Sweek is depressed over the cross. Urara consoles Sweek by mentioning that batsuichi ("One Cross"/"Strike One") is no big deal.
But batsuichi is also slang for... well...
When a person divorces, their name is removed from the family register and replaced with a big cross mark. So "One Cross"/"Strike One" is also slang for a (first-time) divorcee. This term can be similarly extended to "2 Cross", "3 Cross", etc. for N-times divorcees.
(Technically usually only the wife gets struck out on the register, not the husband, but the batsuichi term as slang is unisex and applies equally to either sex.)
So... Urara basically called Sweek a divorcee here without realizing. Hence the reactions from the KSRs. And Sweek herself.
Anyway... I pity the poor soul who's volunteering to translate this pun.
Aside from the pun, the circles and x marks are in reference to the in-game assessments to how well your Umamusume's stats factor into winning a race, double circle is great, circle is good, triangle is okay, and x is bad.
The stats are in order from right to left: Speed/Stamina/Power/Guts/Int. Which means that Spe-chan's Int is really bad lmao.
Edit: I tought about Urara using "being 'X'd'", and the KSRs hearing "beind SEX'd'", but again, it might be too forced.
I thought of using "D" for the X'd grades (with A+/A for the circles), and then "...not like you're a D horse, see?" to pun with "divorcee"... before I realized American English pronounces it differently so it winds up sounding like "D horse, say?" instead.
Oh my, my, my... Who other than me has seen fit to nag you!?
馬の骨 /uma no hone/ - lit 'bone of a horse' n. 'person of doubtful origin';
note that 'nag' as a noun is also a term for a poor-quality horse.Having an X is nothing to worry about, Spe-chan!!
Aaaaawaaughhh!
pbbblt!I really did do my best, but I got an "X" anyway...You're too fat.SWIP!Having an ex...?
You were married, Spe-chan!?
Assessment
But you got a whole bunch of circles! You're amazing, Spe-chan!Don't say that so loud, Urara-chaaan!!