Fix incorrect decimal digits bug #2121

Job	Run time
Test FFI (stable, ubuntu-latest)	34s
Test feature matrix	10m 49s
Lint	36s
Test (stable, macos-latest)	48s
MSRV	36s
Documentation	28s
Test (stable, ubuntu-latest)	35s
Test (stable, windows-latest)	1m 36s
	16m 2s

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