Nic Pothas targeted a minimum first innings total of 450 after contributing to a Rose Bowl record partnership.
The Hampshire wicketkeeper scored 117, his tenth first class hundred for the county, and helped John Crawley put on a record 217 for the fifth wicket as they recovered from 92-4 to 345-5 at stumps.
Pothas said: "We'll be disappointed if we don't get 450 now, that's a minimum, but it was awesome to get to where we are.
"We know we have to get more runs in our first innings, that's been one of our weaknesses in the last couple of years, so to come out at 345-5 aft the end of the first day is a massive result considering where we were."
The 32-year-old added: "It's hard for the umpires because they only see it once, but Michael Carberry was unlucky, the Sky TV replays clearly showed that he missed the ball.
"Jimmy Adams got a good delivery and Dominic Thornely looked like he was seeing it like a football, while Sean could play the same way and get a hundred.
"But because of the situation we were in, John and I had to consolidate and play professionally. We complement each other well, and fortunately we got away with it."
Pothas admitted to being disappointed with himself after he was yorked by AJ Harris in the 91st over.
He added: "I was very unhappy with myself for getting out when I did and exposing Dimi (Mascarenhas).
"It was irresponsible of me, but it's a very good wicket and shows that the groundstaff are getting it right, there's no doubt about that."
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