When properly tuned a CB antenna will have higher reading on Ch 1 and Ch 40, and the lowest reading on Ch 20. Your results indicate that the antenna needs to be longer.
See the Tech Help pages at www.FireStik.com for SWR tuning help. The info applies to all brands and types of CB antennas.
If SWR on channel 1 is greater than that on channel 40, your antenna is considered to be "SHORT" and increasing the physical and/or electrical length of the antenna is required to correct this situation. If the antenna is tunable, move the tuning rod out to make the antenna longer. This condition is can also be corrected by adding a spring and/or quick disconnect to increase the physical height.
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That SWR sounds fine. I would simplify how you tune your CB antenna by just setting the channel to 20 and tuning for the lowest possible SWR there. That will give you the best overall SWR throughout the band. No need to retune it again on other channels like 1 or 40.