Fix incorrect nr calculating

[zyyk78]

Description

fixed incorrect nr and ff calculation (nr incorrect update because ff have been changed)

Fixes # (issue)

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

Branching

• All PRs should be made against the dev branch. The main branch is not often merged back to dev.
• If you want to get your PR out to the world faster (urgent bugfix), poke pgunn to cut a release; this will get it onto github and into conda faster

Has your PR been tested?

If you're fixing a bug or introducing a new feature it is recommended you run the tests by typing

caimanmanager test

and

caimanmanager demotest

prior to submitting your pull request.

Please describe any additional tests that you ran to verify your changes. If they are fast you can also
include them in the folder 'caiman/tests/and name themtest_***.py` so they can be included in our lists of tests.

[zyyk78]

for issue #1480