Trouble converting "Excel time" to "R time"

Question

I have an Excel column that consists of numbers and times that were supposed to all be entered in as only time values. Some are in number form (915) and some are in time form (9:15, which appear as decimals in R). It seems like I managed to get them all to the same format in Excel (year-month-day hh:mm:ss), although the date's are incorrect - which doesn't really matter, I just need the time. However, I can't seem to convert this new column (time - new) back to the correct time value in R (in character or time format).

I'm sure this answer already exists somewhere, I just can't find one that works...

# Returns incorrect time
x$new_time <- times(strftime(x$`time - new`,"%H:%M:%S"))

# Returns all NA
x$new_time2 <- as.POSIXct(as.character(x$`time - new`), 
           format = '%H:%M:%S', origin = '2011-07-15 13:00:00') 

> head(x)
# A tibble: 6 x 8
   Year Month   Day `Zone - matched with coordinate tab`  Time `time - new`        new_time new_time2
  <dbl> <dbl> <dbl> <chr>                                <dbl> <dttm>              <times>  <dttm>   
1  2017     7    17 Crocodile                              103 1899-12-31 01:03:00 20:03:00 NA       
2  2017     7    17 Crocodile                              113 1899-12-31 01:13:00 20:13:00 NA       
3  2017     7    16 Crocodile                              118 1899-12-31 01:18:00 20:18:00 NA       
4  2017     7    17 Crocodile                              123 1899-12-31 01:23:00 20:23:00 NA       
5  2017     7    17 Crocodile                              125 1899-12-31 01:25:00 20:25:00 NA       
6  2017     7    16 West                                   135 1899-12-31 01:35:00 20:35:00 NA