I thought this as well. I am 99% convinced he meant to use "they're"
Thing is the whole concept was a play on words. He had to choose one phrase or the other, i.e:
"see their light" - correct for Cats Eyes
"see they're light" - correct for Cat Size
Because the label was Catsize it naturally felt a bit weird to see "see their light" but I think it was just an error of judgement in deliberately picking such a convoluted tagline rather than any failing in his grammar.... both were correct depending on how you took the product name, the problem was that the product name was extremely close (just missing a space) from one of the two phrases so it feels wrong. But as a point of principle he had to DELIBERATELY choose the 'wrong' grammar in order for users to try and make the connection to Cats Eyes, which wasn't immediately apparent (didn't notice any Cats Eyes on the tin - but maybe I didn't look closely enough).
It took me ages to 'get it', it wasn't until we reached the boardroom when he mentioned double entendres that I finally twigged, oh yeah, he's talking about 'cats eyes' not just 'catsize'. And that in itself is the problem, why it was met with such disdain from his team, because it wasn't an obvious pun or anything that 100% of people would get straight away.
edit: anyway as for the series progression, this week we got a glimpse for the first time of Jim maybe letting his mouth run away with him. He is EXTREMELY good at thinking on his feet, when they are doing pitches he's always the first to come up with an answer to a potentially difficult question. But he started getting into a debate with Lord Sugar and that rarely ends well... sometimes I think you need to just say "ok fair cop guv" and let the dust settle rather than be provocative by fighting back.
Melody seems capable, annoying arrogance although ultimately as I like to say, it isn't arrogance if you really are that ****ing good (remains to be seen).
Tim is easily the most likeable for me, good numbers man with some insightful thoughts but geek tendancies means he struggles to get heard. Sort of candidate that I think may benefit as the process moves on and more candidates are whittled down, meaning he's got more room to show what he can do without getting shouted down.
Leon simply doesn't have what it takes for me, you could tell he wasn't happy about pitching but got railroaded into it, I think Glen was setting him up as the fall guy "nope you don't need to help with anything else, spend the whole day preparing your pitch and make sure you nail it 100%".
Natasha I'm unsure on, seemed to come into her element a bit this week making the commercial, and was clearly noticed by LS as having done well on the task.
Vincent deserved to get fired simply for bringing her back in the boardroom, what a muppet.
Glen I thought had potential until this week but he seemed to be in a situation whereby as PM he felt he had to exert his authority at every opportunity, taking all the decisions and demanding respect from his team. The best PMs are facilitators, not dictators.
Susan - impressed me in early weeks but may be fading
Zoe - quite feisty when she needs to be, time will tell
Edna - not my cup of tea at all, completely failed on the mobile app pitch, very much style over substance I feel
Helen - total nothing candidate, had to look her up on the website to remember she was in it