The symbol
I believe the symbol shown is the "solidus", a symbol for the shilling which evolved over time from a "long s" to an oblique or slash.
In the pre-decimal currency of pounds, shillings, and pence, used in the UK until 1972, it was common to write prices with shillings and pence divided with this mark, so that "2/6" meant "2 shillings and 6 pence". In this notation, two shillings exactly would be written "2/-". Written in cursive script, this would look exactly as shown in your image, with a tall oblique, and the "/-" joined up to the preceding number.
This would make the values "12 shillings" and "10 shillings", respectively. But whose "shilling", and what was it worth in US dollars?
The circulation of multiple currencies
In 1857 an Act was passed in the US Congress officially revoking the legal tender status of foreign coins, which up until then had been encouraged because not enough locally minted coins were available.
The British shilling - a red herring
The most obvious shilling to look at is the British one - worth twelve pence, and one-twentieth of a pound sterling. The exchange rate around this time valued £1 at around $5, which would make a British shilling worth 25 cents. This leads to values of $3 and $2.50, which seem suspiciously high.
The Spanish shilling
The currencies specifically mentioned in the 1857 Act are not British currency, but the Spanish and Mexican dollar. These were the basis of the US dollar, and were widely used at the time at a rate of one-to-one. Notably, it mentions the conventional fractions of this coin, which were not divided into hundredths, like the US Dollar, but halves, quarters, eighths, and sixteenths.
One eighth of a Spanish dollar was called a "real", plural "reales". These appear to have been in common usage at the time, and had various nicknames in different parts of the country (see for instance this article and this quote and discussion). These apparently included "bit", "levy" ... and "shilling".
The value
If taken as one-eighth of a US Dollar, a real would be worth 12.5 cents. (Since a British shilling was worth 12 pence, this multiple may explain the colloquial usage.)
If this is indeed the "shilling" meant by the clerk filling in this form, we would have values of $1.50 for "12/-" and $1.25 for "10/-", which are right in the middle of your ranges from other counties.