My balances are stamped 2230x and the sash weighs 15lbs

A handy person from PA says:
I'm replacing some broken channel balances for some of the windows in my house. I removed the old balances and they are stamped 2230x but I weighted the sashes and they are 15lbs. The shoes seem to match the S370 series so my question is....Should I be getting 2220 or 2230? I felt like the windows were hard to push down but the springs are rusted and very old.
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Donna from SWISCO responded:
The 2230 stamp option is a good choice.
A 23" Series 370 with stamp option 2730 will carry a window sash weight range of 12 through 19 pounds.

Provided information is based on 2 balances per sash. Balances are designed assuming friction in the jamb weather-strip will carry a portion of the sash weight. Suggested sash weights are approximate.
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