The phrase "mild refresh" means making small changes or improvements to something without completely changing it or starting from scratch. Full definition
Small adjustments to creature comforts underpin a relatively mild refresh for Lexus» smallest... (cnet.com)
Given the power boost that the CLA45 got back in September, this relatively mild refresh from Mercedes is entirely justified. (topspeed.com)
Regarding Sony's lineup of VAIO clamshells, alongside mild refreshes for the E, S, and L series, the company is introducing a touchscreen model of its budget ultrabook, the T series. (theverge.com)