Mine is showing 28:14 for the 450mhz sticks and 38:19 for the 330mhz one

Are these numbers ok? Is there anything to configure to improve this?

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(28:14) indicate it take longer time to complete a hashing task (hashing a block header data), which is running slower.
Now, it needs a fast computer to speed up processing, like 8 cores, 16 cores, R7 5800, 6800, R9 5950, threadripper, etc.

(task_ms : scan_ms) 
task_ms:  complete a task time in mil seconds, a average speed measure
scan_ms:  usb stick or compacF  given specific time gap to complete a task.  hashrate higher, this gap time is smaller.

(7:14) or (14:14) indicate the computer can complete a task cycle within usb stick specified time gap, which mean
computer's speed matches usb stick's speed. More sticks need more CPU power.