[Co-staking] - Number to String conversions

[gbarkhatov]

we are doing the number(x) in multiple places for the same variable within this method alone.
If's it's always going to be a number, then we should convert it to number from the top layer.

Originally posted by @jrwbabylonlab in #271 (comment)

The purpose of this ticket is to minimize the conversions of strings to number. Data that we receive for co-staking