I don't have Solaris Pro at hand here but for a close enough example I guess Solaris My Way will do. You should be searching for a line
set tcp.meter.
In Solaris My Way it reads:
set tcp.meter [304.5 2 10 96 1 0 1 1]
1st value sets how far the meter is horizontally from the left edge of the TCP.
2nd value sets the meter distance from the top.
3rd value is the one you are looking for, it's the width of the meter itself.
4th value is the height of the meter.
The last four define how the meter image will act when the TCP is resized.
Try width of 13 as a minimum to get the peak reading visible. You will probably notice soon enough that since the meter is already positioned far right in the TCP, you won't get clear enough reading until you change the position of the meter too, the 1st and maybe also 2nd value.
You will run out of the room on the left soon enough too, the space on that side is limited. Then you may start re-arranging the other images, and making new ones, and...